DIY Tutorial: Build a Portable Air Purifier

Create clean air anywhere with this easy-to-build, luggage-style air purifier

I. Introduction: Clean Air on the Go

Accessing clean indoor air is crucial for our health, but while setting up an air purifier at home is straightforward, it’s much harder in public spaces like offices, meeting rooms, or doctors’ offices. This project aims to change that.

We’ll build a portable, battery-powered air purifier that combines the effectiveness of a high-quality 3M Filtrete furnace filter with the quiet efficiency of PC cooling fans. You can build it either as a rolling luggage-style purifier (wheels + telescoping handle) or as a simpler carry style (regular handle). This tutorial is designed for builders of all skill levels, using common materials and a simple assembly process.

Let’s build something that makes clean air accessible to everyone, everywhere.

The front of the luggage style air purifier showing the filter and telescoping handle.
The front of the luggage style air purifier showing the filter and telescoping handle.
The back and side of the rolling luggage style air purifier, showing the battery, speed control, fans, and wheels.
The back and side of the rolling luggage style air purifier, showing the battery, speed control, fans, and wheels.
The back and side of the simpler carry style air purifier.
The back and side of the simpler carry style air purifier.
Front of the simpler carry style air purifier.
Front of the simpler carry style air purifier.

Table of Contents

II. The Design

Design Goals

  1. Portable: It should be compact and lightweight so that it’s easy to take with you and won’t get in the way.
  2. Battery-powered: It needs to be able to run on battery power long enough to be useful for typical use cases (2 hours minimum).
  3. Powerful, but quiet: It should be able to clean a lot of air quickly, without being obnoxiously loud. You want something that can work quickly when entering a new room, but if it’s too loud, you won’t want to run it at full speed. See also “not embarrassing” below.
  4. Not embarrassing: It should look professional and sleek. To the extent it draws attention (probably unavoidable), we want it to be positive attention. If it looks embarrassing, you won’t want to take it with you.
  5. Affordable and easy to build: It should use cheap, readily available materials and tools where possible, and it should be easy for anyone to build.

Overview

The design is based on a simple rectangular box made out of foam board panels glued together with hot glue.

The box is sized to accommodate a standard 14” × 20” × 1” furnace filter and six 140mm or 120mm PC fans. This size strikes a nice balance between compactness and high airflow.

The PC fans are mounted to the back panel, drawing air through the filter at the front and pushing it out the back. The fans are controlled by a speed controller that also acts as a 12V USB-C PD trigger, allowing the purifier to run at variable speeds off of a compatible USB-C powerbank or wall charger.

Animated view showing how all core components of the design fit together.

The Core Components

Here’s how the core components come together to create clean air:

The Box

The main body is a rectangular box made from ³⁄₁₆” black paper foam board—the same material commonly used for presentation boards and art projects. Foam board is cheap and readily available, plus it’s lightweight, easy to cut, and surprisingly rigid when assembled into a box.

All panels are joined with hot glue, which creates a strong bond and is easy to work with.

The box consists of foam board panels:

  • Fan panel (back): 14” × 20” with six circular cutouts for the fans
  • Two side walls: 3.5” × 20” each
  • Top and bottom panels: 3.5” × 14.5” each (slightly oversized to account for side wall panel thickness)
  • Filter flange: 14” × 20” with the center cut out, leaving a 1⅛” border for the filter to seal against
  • Filter flange spacers: 2” deep foam board strips attached around the inside perimeter of the box to hold the filter flange an even distance from the back fan panel

The Fans & Airflow

Six PC fans mounted on the back panel pull air through the filter and push it out the back of the purifier. PC fans are ideal for this application because they’re:

  • Efficient: Designed to move substantial air while drawing minimal power
  • Quiet: Modern PC fans are engineered for quiet operation
  • Widely available: Easy to source online at reasonable prices

The fans are arranged in a 3×2 grid pattern (three rows of two fans each) to distribute airflow evenly across the entire filter surface.

Wire grills on the outside protect the fan blades from damage and prevent foreign objects (e.g. fingers) from getting caught in the fans.

Power & Electronics

The power system consists of several components:

  1. A compatible USB-C PD powerbank or power supply: Provides the power, but you need one that supports 12V output, which is what PC fans need to run at full speed.
  2. A 12V PD trigger: This component tells the powerbank or power supply to output 12V power instead of the default 5V USB power.
  3. A speed controller: Allows you to adjust fan speeds to balance airflow against noise and battery life.

The Specs

Performance varies significantly based on which fans you choose. The table below compares some common Arctic fan models, using the P14 PWM as a baseline because it offers a good balance of airflow, noise, runtime, and cost. See the Fan Selection section for more details.

Specification P12 PWM
(120mm)		 P14 PWM
(140mm)		 P12 Pro
(120mm)		 P14 Pro
(140mm)
Estimated Airflow (CFM)
6 fans @ 100% speed
airflow calculator		 175 CFM
(82.5%)		 212 CFM 341 CFM
(161%)		 371 CFM
(175%)
Total Fan Weight
6 fans		 1.84 lbs
(−0.73 lbs)		 2.57 lbs 2.45 lbs
(−0.12 lbs)		 3.20 lbs
(+0.63 lbs)
Estimated Runtime
20,000mAh powerbank @ 85% efficiency
6 fans @ 100% speed		 8.5 hrs
(+1.4 hrs)		 7.1 hrs 2.6 hrs
(−4.5 hrs)		 2.4 hrs
(−4.7 hrs)
Perceived Loudness 0.7×
quieter		 1.0× 1.6×
louder		 1.5×
louder
Sound Profile
Listen to the fan recordings		 Moderate whine
Moderate pulsing		 Low whine
High pulsing		 High whine
Low pulsing		 High whine
Low pulsing

The Cost

Total cost for a single build will vary based on fans selected, part availability/pricing, and what materials/tools you have on hand.

Assuming you have all the required tools, you’ll need at a minimum:

  • A Compatible USB-C powerbank — $30–40 (if you don’t have one)
  • 1 filter — $25 (cheaper in multi-packs)
  • Telescoping luggage handle and wheels — $25 (if applicable)
  • Small parts kit — $50 + shipping
  • Foam board — $6
  • Fans — $40–50

Total Cost: $125–200 + tax (more if you need to buy any tools)

Ways to Reduce Costs
  • If you’re missing any tools, borrow them instead of buying them.
  • Single filters are substantially more expensive (per-unit) than multi-packs. Buy them in bulk and save the extras for later or split them with a friend.
  • Consider buying a lower (MPR 1500) or higher (MPR 2200 or 2500) rated filter if you can find them for less (performance may be a little worse though).
  • Arctic fans often come in discounted 5 packs. Sometimes it can be difficult to source a 6th fan at a reasonable price. Consider building a 5-fan variant (with slightly reduced airflow) instead.
  • Shop around for fans and compare different models. Arctic’s Official eBay Store sometimes has “B-stock” or refurbished fans available at a discounted price.
  • If you don’t absolutely need the on-the-go functionality, you can buy a $7 power supply that plugs into your wall and skip the $30 powerbank.

Two Styles to Choose From

This tutorial provides instructions for building two styles, both based on the same core design:

  1. A rolling luggage style air purifier with wheels and a telescoping handle. Extend the handle, tilt it back, and pull it behind you.
  2. A carry style air purifier with a regular handle. Pick it up, carry it around, and set it down.

Rolling Luggage Style

The rolling luggage style has a telescoping handle and roller wheels.

Best for:

  • People who have a hard time lifting or bending.
  • Traveling long distances on foot.
  • Traveling over smooth surfaces.
  • Not going up/down stairs frequently.
  • Using on carpets and rugs (the wheels give it a wider, more stable base)
Specification Value
Overall Dimensions
as pictured including battery		 22 ¾” high × 15 ½” wide × 5 ½” deep
Box Dimensions
only the core foam board box		 20 ⅜” high × 14 ⅜” wide × 3 ½” deep
Weight
with 6 Arctic P14 fans		 6.7 lbs
Typical Cost
for a single build		 $150-$200

Carry Style

The carry style has a simple handle for lifting and carrying.

Best for:

  • Traveling short distances.
  • Traveling over rough terrain.
  • Going up/down stairs frequently.
  • Hard floors (the smaller base makes it less stable on soft surfaces, like carpets or rugs).
  • Around $25 cheaper than the rolling luggage style.
  • Simpler assembly process with fewer parts.
Specification Value
Overall Dimensions
as pictured including battery		 22 ½” high × 15 ½” wide × 4 ” deep
Box Dimensions
only the core foam board box		 20 ⅜” high × 14 ⅜” wide × 3 ½” deep
Weight
with 6 Arctic P14 fans		 5.5 lbs
Typical Cost
for a single build		 $125-$175

Key Design Details

We want to highlight a couple of design details that might seem unintuitive or surprising at first glance and explain why we settled on them:

The Filter Flange

The first version of this air purifier didn’t have a filter flange at all. It used a simple friction fit, with the filter held in place by friction with the inside walls of the box.

It worked, but it required achieving a precision fit:

  • Too tight and you can’t get the filter in.
  • Too loose and the filter falls out.

It’s also very difficult to adjust the fit after you’ve glued the box together, which means a lot of throwaway work if you don’t get it right the first time. But even after you got the fit right, we found that the fit got looser over time as the side walls bowed out more and more.

In other words, the friction fit approach was difficult to get right, and then even when you did, it didn’t hold up well over time.

That’s why we went back to the drawing board and came up with the filter flange design. It tolerates imperfect measurements, maintains an airtight seal regardless of small gaps, and adds structural integrity that prevents the box from deforming.

  • Creates an airtight seal: Weather stripping applied around the inner edge of the flange creates an airtight seal with the filter, regardless of any gaps between the filter and the sides of the box. This allows us to make the box slightly larger than the filter, leaving us some wiggle room so we don’t have to worry about getting the sizing perfect.
  • Provides a mounting surface: Velcro patches in the corners are used to securely hold the filter in place while still allowing for easy removal and replacement.
  • Adds structural rigidity: The flange acts as an internal frame that stiffens the box and keeps the side walls from bowing outward over time.

It’s more work to cut out and assemble, but we think it makes for a more forgiving design that holds up better over time.

Compactness vs. Stability

The Challenge: We want the air purifier to be as compact as possible for easy transport, but the small base makes it inherently less stable. This is exacerbated by the fans (the heaviest components) being mounted at the back, which makes the air purifier particularly prone to tipping over backward, especially on soft surfaces like carpets and rugs.

Even though the carry-style air purifier was the initial design, we ended up releasing the rolling luggage-style instructions first, because the wheels ended up solving the stability issue by creating a larger base.

We held off on releasing the carry-style air purifier instructions until we came up with a solution that worked for the carry-style design. We didn’t want to make the box bigger or add unnecessary weight to the base as this would run counter to the design goals.

Due to the uneven weight distribution, we were able to place the carry handle closer to the back of the air purifier. This made carrying it easier, because you didn’t have to exert extra effort by holding it further away from your body when walking. We really wanted to preserve this benefit, so we also ruled out extending the base further backward beyond the fans, since it would mean you’d have to hold it further away from your body.

The Solution: tilting the air purifier forward by about 5 degrees (raising the back about 0.3” above the front). This small tilt shifts the center of gravity forward, increasing stability and reducing tipping risk, without adding much bulk or weight.

But we couldn’t find a cheap, easy-to-source part that had the right size and angle. In the end we resorted to having custom angled plastic feet 3D printed for us so that we could include them in the small parts kit.

If you’re building the carry version without buying the small parts kit, there are a lot of ways you could address the stability issue:

  • Make the bottom panel 4” deep and extend it out past the base of the fans (but you might want to add vertical supports to it so it doesn’t just bend).
  • Using different thickness of adhesive rubber feet for the front and back (but most rubber feet are tapered, so this will slightly reduce the effective footprint, reducing stability).
  • Glue plastic shims or wedges to the bottom panel:
    • These shims add the perfect tilt, but aren’t quite long enough to fully protect the bottom panel (they’d probably work okay, but the front foam board edge would touch the ground).
    • These shims are the perfect length, but only add a 3-degree tilt (which would still help substantially).
  • Glue stuff to the back edge to raise it.

There are a ton of possibilities here and we encourage you to experiment with different design choices. If you try out any alternative approaches, we’d really like to hear about it!

III. Photo Gallery

The front of the luggage style air purifier showing the filter and telescoping handle.
The front of the luggage style air purifier showing the filter and telescoping handle.
The back and side of the rolling luggage style air purifier, showing the battery, speed control, fans, and wheels.
The back and side of the rolling luggage style air purifier, showing the battery, speed control, fans, and wheels.
The back and side of the simpler carry style air purifier.
The back and side of the simpler carry style air purifier.
Front of the simpler carry style air purifier.
Front of the simpler carry style air purifier.
Front view of the original carry style prototype. This design was particularly prone to tipping over backwards due to the uneven weight distribution created by the fans. This design was slightly thinner at only 3" thick.
Front view of the original carry style prototype. This design was particularly prone to tipping over backwards due to the uneven weight distribution created by the fans. This design was slightly thinner at only 3” thick.
Side view of the original carry style prototype.
Side view of the original carry style prototype.
Inside the original carry style prototype. Note the lack of a filter flange. This design relied on percise sizing to create a tight seal with the filter. In this design, the filter is only held in place with friction. The box has gotten looser over time, leading to filter falling out more often and gaps around the edges of the filter.
Inside the original carry style prototype. Note the lack of a filter flange. This design relied on percise sizing to create a tight seal with the filter. In this design, the filter is only held in place with friction. The box has gotten looser over time, leading to filter falling out more often and gaps around the edges of the filter.
The original carry style prototype, retrofitted with angled feet for improved stability. The angled feet pitch the airpurifier forward 5 degrees, moving the center of mass away from the back edge and improving stability.
The original carry style prototype, retrofitted with angled feet for improved stability. The angled feet pitch the airpurifier forward 5 degrees, moving the center of mass away from the back edge and improving stability.
Rear view of the original carry style prototype, retrofitted with angled feet for improved stability. Packing tape was applied to around the edges of the foam board to help reduce separation of the foam board and the paper liner and improve durability.
Rear view of the original carry style prototype, retrofitted with angled feet for improved stability. Packing tape was applied to around the edges of the foam board to help reduce separation of the foam board and the paper liner and improve durability.
A beta tester's rolling luggage style build with printed vinyl wrap applied to the foam board. The wrap was applied before cutting the foam board to shape.
A beta tester’s rolling luggage style build with printed vinyl wrap applied to the foam board. The wrap was applied before cutting the foam board to shape.
A beta tester's rolling luggage style build with printed vinyl wrap applied to the foam board and the telescoping luggage handle extended.
A beta tester’s rolling luggage style build with printed vinyl wrap applied to the foam board and the telescoping luggage handle extended.
Front view of a rolling luggage style build made out of heavy duty, plastic-faced Ultraboard Classic. This material is more durable than paper-faced foam board, but is harder to source and much more difficult to work with.
Front view of a rolling luggage style build made out of heavy duty, plastic-faced Ultraboard Classic. This material is more durable than paper-faced foam board, but is harder to source and much more difficult to work with.
Rear view of a rolling luggage style build made out of heavy duty, plastic-faced Ultraboard Classic with an Aranet CO2 meter attached.
Rear view of a rolling luggage style build made out of heavy duty, plastic-faced Ultraboard Classic with an Aranet CO2 meter attached.
A rolling luggage style build made out of heavy duty, plastic-faced Ultraboard Classic with the telescoping luggage handle extended.
A rolling luggage style build made out of heavy duty, plastic-faced Ultraboard Classic with the telescoping luggage handle extended.

IV. Materials and Tools

Bill of Materials (BOM)

Small Parts

Buy on Etsy — $50

The following items are available to purchase together in our small parts kit, saving you from having to buy them individually at a higher cost. Before ordering the small parts kit, you’ll need to decide what size fans you’ll be using and whether you will be making the rolling luggage style or the simpler carry style air purifier.

Item Qty Links Notes
PC Fan Speed Controller 11 AliExpress: 1 Make sure to get the PD version. The label should say:
12V(PD/QC)
TYPE-C(C to C)
4-pin PC Fan 1-to-3 Splitter Cables 2*2* Amazon: 2-pack, 5-pack *Only needed for non-PST fans. PST fans have an additional connector that allows them to be daisy chained.
Fan Grills 66

140mm

120mm

 Choose based on your fan size selection.
8” Mini Hot Glue Sticks 44 Amazon: 25-pack We recommend extra-long (8”), extended working time glue sticks. These reduce the need for mid-project reloading and give you more time to align pieces before the glue hardens.
Adhesive Velcro Patches (¾”–1”) 88 Amazon: 10-pack For attaching the filter and battery. Can be cut to size as needed.
³⁄₁₆” × ⅜” Open Cell Foam Weather Stripping 6ft 6ft Amazon: 17ft roll Low-density, high-compressibility foam works best.
6”–12” USB-C Cable 11 Amazon: 3-pack (6”) Short cable to connect powerbank to speed controller. Or use a twist tie to shorten a longer cable.
¾”–1” Adhesive Rubber Feet 20 Amazon: 20-pack Needed to raise the front corners of the air purifier so the screws attaching the wheels don’t scrape the ground.
2” × #8-32 Screws 2424 Amazon: 100-pack 4 per fan. You can substitute M4 (or #6-32 in a pinch) screws, as long as they are between 1⅝” and 2⅜”, as long as you get matching nuts. Flat-head or pan-head screws work best here.
1” × #8-32 Screws 60 Amazon: 100-pack 4 for mounting the luggage handle and 2 for the back of the wheels (the bottom of the wheels need special low-profile screws to prevent them from scraping the ground). To save money, you can use the same screws as above, although they’re longer than you need. We don’t recommend using #6-32 for the luggage handle, as the luggage handle screw holes are substantially bigger than the fan screw holes.
#8-32 Nuts 3024 Amazon: 100-pack One for each #8-32 machine screw.
16mm M4 Low-profile Machine Screws 40 Amazon: Assorted
AliExpress: 30-pack 		Low-profile screws for mounting the bottom of the wheels to keep them from scraping the ground. Cabinet pulls/handles often come with relatively low-profile M4 screws, so you may have some extras lying around.
M4 Nuts 40 Amazon: 100-pack One for each M4 machine screw.
#8 × ¾” Fender Washers 3424 Amazon: 50-pack Fender washers help distribute the load of the screw head over a larger area of the foam board. This allows you to get a tighter fit without crunching the foam board.
½” Sheet Metal Screw 10 Hardware store For re-securing the bottom bracket of the luggage handle after shortening the tube.
#10 × 1” Fender Washers 04 Amazon: 50-pack To save money you can use the #8 × ¾ fender washers instead, but the 1” washers will better distribute the load from the handle.
Cabinet drawer handle with screws 01 Amazon: 12-pack
Angled Plastic Feet 02 Included in our small parts kit

Needed to tilt the carry air purifier forward slightly to improve stability. The fans add a lot of weight toward the back of the air purifier and make it prone to tipping over in that direction. The angled feet help counteract that tendency without adding bulk or weight.

If you aren’t purchasing our small parts kit, you can easily makeshift something.
Black Gaffer Tape or Duct Tape (6–12”) Optional Amazon: 1 For making pull tabs for the filter.
Adhesive Cable Clips Optional Amazon: 30-pack To make it easier to route the wires and keep them away from the fan blades.

Large Parts

Item Qty Links Notes
3M Filtrete 1900 14” × 20” × 1” Furnace Filter 11 Available cheaper in bulk, e.g. 6-packs on Amazon.
³⁄₁₆” Black Paper Foam Board (20” × 30”) 22

2 sheets will leave you with about a half sheet of extra foam board in case you make mistakes.
Telescoping Luggage Handle 10 Amazon: 1, 2 You can find other identical listings on Amazon by searching for “replacement telescoping luggage handle”. This design appears to be the most common single tube telescoping luggage handle.
Roller Wheels 20 Amazon: 2-pack, 4-pack There are other identical listings on Amazon, but pay attention to the wheel size (1.5”) since there are multiple sizes of this design.

Fan Selection

This tutorial is designed for either 120mm or 140mm PC fans. There are many different models of PC fans to choose from.

Below we’ve listed some fans from Arctic that we have experience with. Arctic fans are generally considered to be an economical option (good performance for the price), especially since many Arctic fans come in discounted 5-packs. If you want to avoid buying a 6th fan, you can build the air purifier with only 5 fans (just don’t cut one of the fan holes).

Different fans will have different prices, airflow, weight, energy use, and noise profiles. We provide some of these stats and example noise clips below.

Model Estimated Airflow
(CFM)		 Stats Notes
Arctic P12 PWM (120mm) 5 fans: 159.3
6 fans: 174.7		 139g
0.1A
Arctic P12 Max (120mm) 5 fans: 286.3
6 fans: 312.5		 184g
0.29A

Discontinued, but some stock may still be available at higher prices.

*Add multiple to cart to get accurate shipping estimate.
Arctic P12 Pro (120mm) 5 fans: 298.8
6 fans: 340.6		 185g
0.33A
Arctic P14 PWM (140mm) 5 fans: 194.9
6 fans: 211.5		 194g
0.12A
Arctic P14 Max (140mm) 5 fans: 304.2
6 fans: 328.3		 245g
0.35A

Discontinued, but some stock may still be available at higher prices.

*Add multiple to cart to get accurate shipping estimate.
Arctic P14 Pro (140mm) 5 fans: 346.8
6 fans: 371.0		 242g
0.35A
Listen to Fan Sounds

One of the most important parts of selecting a fan model is finding one that you don’t mind the sound of. If you can’t stand the sound of the fans you select, you aren’t going to want to run the air purifier (at least not at full speed).

To make it easier to compare fan models, we recorded sound clips for the various Arctic fans we have access to. All clips were recorded under the same conditions, using an iPhone 16 Pro placed 3 feet away from the fan, with the fan running at full speed and blowing away from the microphone.

Click on a fan model below to hear what it sounds like, then use the play button to start/stop the audio:

Arctic P12 PWM Arctic P12 Max Arctic P12 Pro Arctic P14 PWM Arctic P14 Max Arctic P14 Pro

P14 selected

Powerbanks & Power Supplies

Powerbanks are tricky for a few reasons:

  1. You need to find a powerbank that supports 12V output. 12V output is an optional part of the USB-C PD spec, so not all chargers and powerbanks support it.

  2. Many powerbanks that support USB-C PD output have a “feature” where pressing the power button will force them down to 5V output. This probably won’t hurt the fans, but it will make them run extremely slowly or not at all. I try to avoid any powerbanks that have this “feature”, because it makes the air purifier less reliable.

  3. Your powerbank needs to be able to supply enough current at 12V to power the fans you choose. The USB PD specification sets a limit of 12V/3A, but some powerbanks will be even lower than this, e.g. 12V/1.5A (18W) or 12V/1.67A (20W).

    Note that the maximum current drawn by a fan at startup may briefly exceed its rated current, so you need to leave some headroom. For example, the Arctic P14 Max is rated at 0.35A so 6 fans should draw 2.1 amps, but the maximum startup current can hit 3.3A, above the 3A limit of the USB PD specification. Some powerbanks do not tolerate over current conditions like this and will cut power completely when this happens.

    If this is an issue with your combination of fans and powerbank or charger, you may be able to work around it by using the speed controller to slowly ramp up the fan speed when turning it on—or you can try to find a powerbank that’s more tolerant of over current conditions.

I haven’t experienced either of the above issues with the powerbanks listed below, all of which have been tested with 6 Arctic P14 Max fans:

Power Bank Notes
VEEKTOMX 20000mAh 100W Reasonable price and size.
Henhot 20000mAh 65W Smaller and lighter weight than the above, but a little more expensive.

Here are some options for power supplies if you want to be able to use a wall outlet to run the air purifier continuously:

Power Supply Notes
100w USB-C Power Supply Tested with 6 Arctic P14 Max fans.
MeLE 12V/3A USB-C Power Supply Compact size, but more expensive. Tested with 6 Arctic P14 Max fans. Note that this power supply only outputs 12V power. It doesn’t do USB-C PD voltage negotiation, so it’s not safe to use with regular USB-C devices.
65w USB-C Power Supply Cheaper option. Haven’t tested this particular model, but it should work. You can find any number of these on Amazon. Just make sure you can see in the picture or listing details that it supports 12V/3A output and that it has a USB-C connector.

Tools

Required Tools

Tool Recommendations Notes
Hobby knife (e.g., X-Acto) with fresh blades Westcott Carbo Titanium Craft Knife If you don’t have a hobby knife, you can also use a utility knife, but it may be harder to get clean cuts, especially if you are cutting the fan holes by hand.
Metal ruler or straightedge At least 20 inches long, for cutting the foam board straight (hopefully).
Pencil and marker For marking cuts.
Painter’s tape or Scotch tape For attaching the printed fan template pages to the foam board panel.
Scratch awl, ⅛” drill bit, or other small pointy object For making the screw holes.
Hot glue gun For gluing the foam board pieces together.
Power drill and drill bits Only needed to drill a screw hole in the bottom of the telescoping luggage handle to secure the bottom bracket after shortening the tube. You could probably MacGyver some other way of affixing the bracket (like using 5-minute epoxy) if you don’t have access to a drill.
Hacksaw To shorten the telescoping luggage handle.
Phillips screwdriver

Optional Tools

Tool Links Notes
Logan FoamWerks or Cos-Tools Foam Board Cutting Tools Using a dedicated foam board cutter with a rail makes cutting easier and more precise, but it’s also fine to use a hobby knife if you don’t want to buy extra tools.
Circle Cutter A circle cutter will cut clean, near-perfect fan holes with minimal effort. Using a hobby knife is possible but requires a steady hand and a lot of patience to get a good result. Consider whether the tool purchase is worth it for your skill level and how often you might use it.
Self-healing cutting mat If you don’t already have one, you can use several layers of scrap cardboard. Just be careful not to cut all the way through.
Parchment paper To provide a work surface that the hot glue won’t stick to.

V. Before You Begin

  1. Read through all the instructions once before starting. This will help you understand the overall process and identify any tools or materials you might be missing.
  2. Find a large, flat work surface. Ideally one that you don’t mind getting scratched up or getting hot glue on, like a workbench. You can also protect your work surface with a cutting mat or several layers of scrap cardboard.

VI. The Build—Step-by-Step Instructions

Part 1: Preparing the Foam Board Panels

Step 1: Cut the Foam Board Pieces

The first step is to cut all the foam board pieces.

But first, here are some tips on how to cut foam board like a pro:

Cut the Foam Board to Size
  • Cut 2 pieces at 14” × 20”. These will become the fan panel (back) and the filter flange.
  • Cut 2 pieces at 3 ½” × 20”. These will become the side walls.
  • Cut 2 pieces at 3 ½” × 14 ½”. These will become the top and bottom panels.
  • Cut 1 piece at 2” × 20”. This will become the filter flange spacers.
Foam board pieces cut to size with labels showing dimensions
Foam board pieces cut to size with labels showing dimensions
Cut out the Filter Flange

Take one of your 14” × 20” foam board pieces and cut out the center, leaving a 1 ⅛” border on all sides. This will be the filter flange. The filter flange will provide a surface for the filter to seal against and will add torsional stiffness.

Use your straight-edge and hobby knife to cut out the center of the filter flange.
Use your straight-edge and hobby knife to cut out the center of the filter flange.
The filter flange that creates a seal between the filter and the box
The filter flange that creates a seal between the filter and the box
Cut out the Filter Flange Spacers

Take your 2” × 20” foam board piece and cut it into 8 pieces of roughly equal length. Each piece will end up being 2” by about 2 ½”. It’s not important that all the lengths are exactly the same. These pieces will be the filter flange spacers, which will help support the filter flange while you glue it in place.

8 filter flange spacers cut from the 2” × 20” foam board piece, each about 2” by 2 ½”.
8 filter flange spacers cut from the 2” × 20” foam board piece, each about 2” by 2 ½”.

Step 2: Print and Apply the Fan Template

Download the fan template for your chosen fan size and build style.

Rolling luggage style

To make it easy to print at home, each fan template contains 4 overlapping 8½” × 11” pages: one page for each corner of the fan panel, labeled top left, top right, bottom left, and bottom right.

  1. Print each page on its own sheet of 8 ½” × 11” paper.
  2. Set your printer to print at 100% scale or Actual Size.
    • Do not use “Scale to Fit” or “Fit to Page”.
    • Do not attempt to do a borderless print.
  3. Note that the edges of the template will get cut off by your printer’s margin. This is expected and okay! The edge markings are not important for the build.
  4. Important: Do not cut or trim the edges of the template after printing it!
Align and Secure the Template Pages to the Fan Panel

The four pages of the template are labeled with top left, top right, bottom left, and bottom right. This indicates the corner of the fan panel the page should be applied to.

  1. Take your 14” × 20” piece of foam board and lay it on a clean, flat surface.
  2. Working one template page at a time, align the corner of the page with the corresponding corner of the fan panel. The edge of the paper and the edge of the foam board should be flush with each other. Use painter’s tape or Scotch tape to secure all four corners of the page to the foam board. This will prevent it from slipping around while you work. Repeat with the remaining template pages
  3. The template pages will overlap in the middle of the foam board. Make sure the overlapping lines match up.
One template page taped to the fan panel
One template page taped to the fan panel
Two template pages taped to the fan panel
Two template pages taped to the fan panel
Three template pages taped to the fan panel
Three template pages taped to the fan panel
Four template pages taped to the fan panel
Four template pages taped to the fan panel
Taping the template pages to the fan panel on a rolling luggage style build.

Step 3: Mark the Screw Holes and Fan Centers

Now, we’ll transfer the fan and hardware locations to the fan panel.

Use a sharp pointy object (like an awl or a nail) to transfer the screw hole locations and fan center points from the template to the foam board by firmly pressing through the template and into the foam board.

Once you’ve transferred all the holes to the foam board, take a second look to make sure you got them all—it’s really easy to miss one or two.

Using an awl to mark screw holes through the template on a rolling luggage style build.
Using an awl to mark screw holes through the template on a rolling luggage style build.
The fan panel with the templates removed. The six fan center points have been highlighted using a metallic Sharpie.
The fan panel with the templates removed. The six fan center points have been highlighted using a metallic Sharpie.

Step 4: Cut the Fan Holes

You have two options for cutting the fan holes:

  1. Cutting the fan holes with a circle cutter (recommended)
  2. Cutting the fan holes by hand
Option 1: Cutting the Fan Holes with a Circle Cutter (Recommended)

Carefully remove the template from the foam board, taking care not to tear the foam board when removing the tape.

Set your circle cutter to the appropriate size for your fans:

  • 58mm radius for 120mm fans
  • 67mm radius for 140mm fans

Once you’ve set the size of your circle cutter, test it on some scrap material. Line up one of your fans with the hole in the scrap material and compare the size of the hole with the fan to make sure the sizing is correct. Adjust the size of your circle cutter and repeat the test until the cut hole matches your fan.

When you’re ready to start cutting, place the pivot point of the circle cutter into a center mark. Depending on your cutter model, you may need to either extend the blade or apply steady pressure as you rotate it. Make several passes until you achieve a clean cut. Repeat for all six holes.

Using a circle cutter to cut the fan holes on a rolling luggage style build.
Option 2: Cutting the Fan Holes by Hand

If you don’t have a circle cutter, you can cut the holes with a sharp hobby knife. With the template still attached, carefully cut along the circular lines, going through both the paper and the foam board.

Once you’ve cut all 6 fan holes, carefully remove the template from the foam board, taking care not to tear the paper when removing the tape.

Part 2: Assembling the Purifier Box

An assembled view showing all of the foam board pieces put together.
An assembled view showing all of the foam board pieces put together.
An exploded view showing how all of the foam board pieces fit together.
An exploded view showing how all of the foam board pieces fit together.

Step 5: Glue the Box Together

Now we’ll assemble the box. We’ll start by gluing the two side wall panels to the fan panel, and then we’ll glue on the top and bottom panels.

But first, here are some tips that might help if you’re not already a hot glue pro:

Glue on the Side Walls

Place your fan panel and one 3.5” × 20” side wall flat on your work surface.

You want to attach the side wall to the fan panel at a 90-degree angle, with the paper side of the side wall touching the cut foam edge of the fan panel.

Run a bead of hot glue along one 20” edge the side wall. The bead of glue should be touching the paper side of the side wall—not the cut foam edge.

Press the glued edge of the side wall against the cut foam edge of the fan panel, holding it at a 90-degree angle. If you have something square, you can hold it against the outside of the side wall while the glue hardens to help you get a 90-degree angle. Take care to ensure the top and bottom edges of the side wall are aligned with those of the fan panel before the glue hardens.

Repeat with the other side wall panel.

Gluing the side walls to the fan panel on a rolling luggage style build.
Glue on the Top and Bottom Panels

Place the top and bottom panels flat on your work surface. Just like with the side walls, you want to attach the top and bottom panels to the fan panel at a 90-degree angle, with the paper side of the top and bottom panels touching the cut foam edge of the fan panel and the side walls.

Remember that we made the top and bottom panels slightly longer (14 ½” instead of 14”) so that they would be long enough to overlap the side walls (with an extra ⅛” to account for any imperfections or small misalignments). Any extra can be carefully trimmed off with your hobby knife after you’ve finished gluing the panels in place.

Run a bead of hot glue along one of the 14 ½” edges and both of the 3 ½” edges. Just like with the side walls, the bead of glue should be touching the paper side of the top/bottom panel—not the cut foam edge.

Press the glued edge of the top/bottom panel against the cut foam edge of the fan panel and the cut foam edges of the side walls. Take care to ensure the edges of the top/bottom panel completely cover the edges of the side walls.

Repeat for the other panel.

Gluing the top and bottom panels to the fan panel on a rolling luggage style build.

Step 6: Glue the Filter Flange Spacers into Place

Now we’re going to glue the 8 filter flange spacers into position inside the box. These spacers will act as a built-in jig to ensure the filter flange is installed at a level depth all the way around. They’ll also reinforce the box where the wheels attach for the rolling luggage style and where the handle and feet attach for the carry style.

We’re going to position the spacers roughly equidistant around the interior of the box. Place the spacers horizontally, with the long 2 ½” edge parallel to the fan panel. The spacers should extend 2” up the side walls.

For the rolling luggage style build, place the filter flange spacers as follows:

Bottom panel spacers (2)

Place a spacer in each corner of the bottom panel.

For the bottom panel spacers, we want to place them so that they’ll line up with the wheel screw holes later on to provide extra reinforcement.

Side wall spacers (4)

Place two spacers on each sidewall so that they are roughly equidistant from each other and each end.

Top panel spacers (2)

Place a spacer 1” in from each corner of the top panel.

For the top panel spacers, we need to leave room for the fan speed controller in the corner and the luggage handle bracket in the middle.

For the carry style build, place the filter flange spacers as follows:

Bottom panel spacers (2)

Place a spacer in each corner of the bottom panel.

For the bottom panel spacers, we want to place them so that they’ll line up with the foot screw holes later on to provide extra reinforcement.

Side wall spacers (4)

Place two spacers on each sidewall so that they are roughly equidistant from each other and each end.

Top panel spacers (2)

Measure the distance between the screw holes on your carry handle.

  • 5–6” → place the spacers 3” in from each corner.
  • 6–7” → place the spacers 2 ½” in from each corner.
  • 7–8” → place the spacers 2” in from each corner.
  • Or just use your handle as a guide: center your handle horizontally on the top panel and align the center of each spacer with the handle’s screw holes.

For the top panel spacers, we want them to line up with the carry handle screw holes later on to provide extra reinforcement. We also need to leave room for the fan speed controller in the corner.

The eight filter flange spacers in position on a carry style build. Note the asymmetry between the top and bottom positions.
The eight filter flange spacers in position on a carry style build. Note the asymmetry between the top and bottom positions.

It’s important that the spacers sit flush against the fan panel in order to provide a level surface for the filter flange. Check to see if any excess glue along the seams is getting in the way of the spacers sitting flush against the fan panel.

If you find any excess glue interfering with the spacers, you can use the tip of your hot glue gun to melt the excess glue and push it out of the way or you can add a bevel to the edge of your spacers to make space for the glue.

Optional: Bevel the Spacers

If you find that some of your spacers aren’t sitting flush with the fan panel because of excess glue, you can use your hobby knife to cut a small bevel into the long 2 ½” edge of each spacer. The bevel should only cut through the paper on one side of the foam board and only extend part way through the foam edge.

When installing the spacers, place the beveled edge against the seam so that there’s extra room for the glue.

Cutting a small bevel into the long edge of the filter flange spacers.
Cutting a small bevel into the long edge of the filter flange spacers.
The beveled edge of a finished filter flange spacer.
The beveled edge of a finished filter flange spacer.

Glue each of the spacers to the inside of the box, making sure they’re sitting flush against the fan panel before the hot glue sets.

Gluing the eight filter flange spacers into place on a carry style build.

Step 7: Seal the Seams

Once you’re done gluing all 8 spacers into place, check that all of the interior seams of the fan panel have visible glue.

Run a bead of hot glue along any areas that don’t. This ensures the box is fully sealed.

Congratulations, you’ve completed the box assembly!

Your work has been approved by the supervisor!
Your work has been approved by the supervisor!

Part 3: Installing the Handle

Step 8: Shorten the Telescoping Luggage Handle

The goal is to shorten the handle’s main tube from its original 15” length to 14 ⅛”. This is necessary because the handle is too long to fit 6 fans into the box as-is.

Removing the Bottom Bracket

Start by removing the bottom bracket from the handle.

The procedure for removing the bracket depends on whether the bottom bracket of your telescoping luggage handle is secured with a screw or a metal catch. Inspect yours and follow the appropriate steps.

Style 1: Screw Type

This type of handle has a small screw securing the bottom bracket to the tube. Simply use a screwdriver to remove the screw holding the bracket to the tube and slide the bracket off.

Style 2: Metal Catch Type

This style is much more difficult to remove. You’ll need to carefully pry the plastic bracket up and away from the tube until it can slide over the metal catch holding it in place.

Measure and Cut

Measure 1” up from the end of the tube and mark the tube with a Sharpie.

To get an even line all the way around the tube, slide the bottom bracket back onto the tube until it just reaches the mark and use the edge of the bracket to trace a line all the way around the tube. If you have the metal catch type, be careful not to slide the bracket on too far or you’ll have to go through the removal process all over again!

Slide the bottom bracket roughly ¼” down from the line to give yourself room to make the cut. We leave the bottom bracket part way on the tube to help stabilize the tube while we cut it.

Elevate the handle a little ways above your work surface by putting some pieces of scrap wood (or other risers) underneath the top and bottom brackets. The extra vertical space will make it easier to operate the hacksaw without it hitting the work surface.

Use a hacksaw to carefully cut the tube at the line. It’s okay if the cut isn’t very straight or even—that’s why we took off 1” of material when we only needed to shorten the tube by ⅞”.

Using a hacksaw to shorten the bottom end of the luggage handle tube by 1”. Note that the tube is elevated on blocks and the bottom bracket is partially re-seated to help keep the tube stable during the cut.

Once you’ve cut through the tube, remove the cut piece of tube from the bottom bracket and carefully clean up any metal filings on your work surface or inside the tube.

Slide the bottom bracket onto the bottom of the tube and measure the length of the tube from the top of the top bracket to the bottom of the bottom bracket. Slide the bracket up or down until the overall length is 14 ⅛”. If the overall length is over 14 ⅛”, try wiggling the bracket back and forth to make sure it is fully seated. If it’s still over 14 ⅛”, you’ll need to shorten the tube some more. If you have a metal file, filing down the end of the tube may be easier than trying to make a very thin cut.

We’ll fine tune the length of the handle to fit the fan placement and then secure the bottom bracket permanently with a screw in a later step. In the meantime, we need to keep the bottom bracket accessible so that we can use it as a template for cutting out the hole in the top of the box that the handle will extend through.

Step 9: Cut the Hole for the Telescoping Luggage Handle

Trace the Handle Hole
  1. Remove the bottom bracket from the luggage handle.
  2. Notice that one end of the bracket has a lip on it to keep the tube from sliding all the way through the bracket. Place the side without the lip against the inside of the top panel. You want to trace this side of the bracket because it will give you a slightly larger hole than the side with the lip.
  3. Make sure the bracket is positioned exactly in the center of the top panel by measuring the distance between each edge of the bracket and the side walls.
  4. Use a pencil to trace the inside opening of the bracket onto the foam board. This will be your guide for the handle cutout.
Tracing the hole for the luggage handle.

Slide the bottom bracket back onto the luggage handle tube once you’re done tracing the hole.

Cut the Hole

Use your hobby knife to carefully cut out the hole for the handle. It’s better to start small and then enlarge the hole later if necessary. We’ll test the fit below.

The mark showing where to cut the hole for the telescoping luggage handle.
The mark showing where to cut the hole for the telescoping luggage handle.
Cutting the hole for the telescoping luggage handle.
Cutting the hole for the telescoping luggage handle.
The hole cut out for the telescoping luggage handle.
The hole cut out for the telescoping luggage handle.
Remove the Grip from the Handle

Fully extend the handle until it locks, then partially retract the handle until it looks like this. You should be able to see all three telescoping tubes.

The handle, slightly extended, with all three telescoping tubes visible. When testing the fit below, you'll need to make sure you test both the inner and the middle tube.
The handle, slightly extended, with all three telescoping tubes visible. When testing the fit below, you’ll need to make sure you test both the inner and the middle tube.

Taking care not to collapse the handle, remove the two screws (one on each side) that secure the grip to the tube. Put the screws in a ziploc bag so that you don’t lose them. Then slide the grip out of the tube and remove the plunger rod from inside.

Removing the grip of the telescoping luggage handle.
Test the Fit

Once you’ve removed the grip, place the handle inside the box and try to slide the telescoping tube assembly through the hole to check the fit. Move slowly and take care not to accidentally collapse the tube while checking the fit.

If the fit is too tight, carefully enlarge the hole and test again. Only cut away a little material at a time. If you cut away too much material, there’s no way to put it back!

Testing the fit of the luggage handle hole. Note that the video doesn’t show testing the middle tube, which is important!
Seal Around the Hole

Once the hole is sized correctly, apply foam weather stripping around the hole on the inside of the top panel. This will help create a seal between the handle bracket and the hole and prevent air leaks.

You’ll need to use scissors to cut an extra thin strip of weather stripping for the bottom edge.

Some of the foam will be visible from the outside through the hole, so we recommend using dark-colored foam if available to better match the color of the foam board. This isn’t an issue for the weather stripping we’ll apply to the filter flange later on.

Foam weather stripping applied around the edge of the luggage handle hole on the inside of the box.
Foam weather stripping applied around the edge of the luggage handle hole on the inside of the box.

Step 10: Attach the Telescoping Luggage Handle

Mount the Handle

Place the handle inside the box and slide the telescoping tube assembly through the hole in the top panel.

Turn the box over and place a #8 × ¾” fender washer over each of the four handle screw holes on the back of the box. Then insert a #8-32 × 1” screw into each hole.

Line up the holes in the luggage handle brackets with the screw holes in the box. Remember to slide the bottom bracket up or down on the tube as needed to align with the bottom screw holes.

Once everything is aligned, secure each screw with a #8-32 nut. Make sure not to overtighten and crush the foam board!

Installing the luggage handle with washers and screws visible on the outside. Ignore the filter flange for now—you'll install it later.
Installing the luggage handle with washers and screws visible on the outside. Ignore the filter flange for now—you’ll install it later.
Installing the luggage handle with nuts visible on the inside. Ignore the filter flange for now—you'll install it later.
Installing the luggage handle with nuts visible on the inside. Ignore the filter flange for now—you’ll install it later.
Reassemble the Handle

With the handle now mounted, re-insert the plunger rod and re-attach the grip to the tube with the two screws you removed earlier.

Note that the screw holes on the front and back of the handle are at different heights. Examine the screw holes on your grip before reinserting it to make sure it’s oriented the same way as before. This will make it easier to screw the screws back in, since the screws won’t have to cut new threads into the plastic.

Secure the Bottom Bracket

Use a power drill and a small drill bit to drill a hole through the bottom bracket and into the aluminum tube.

  • Make sure to drill your hole below the telescoping parts—you should be fine as long as you put your hole roughly a third of the way up from the bottom of the bracket.
  • Only drill through the top layer of the bracket and tube, about ¼” deep, until your drill bit hits air.

Clean up the metal and plastic filings inside and around the tube. Then use a screwdriver to screw a ½” Sheet Metal screw into the hole and secure the bottom bracket to the tube.

Securing the bottom bracket to the aluminum tube with a sheet metal screw (shown outside the air purifier box).
Optional: Stabilizing the Handle

Depending on the size screw you used to attach the handle, there may be enough ”play” in the screw holes for the handle to shift back and forth slightly—enough that the telescoping tubes may catch on the sides of the hole when extending the handle.

You can test this out by collapsing the handle, firmly holding the box, and using the grip to try to shift the handle left or right. If the handle shifts easily or if any of the telescoping tubes catch on the sides of the hole when you extend the handle, you can stabilize the handle brackets with some hot glue:

  1. Fully extend the handle.
  2. Shift the handle brackets so that the handle is centered in the hole.
  3. Use your hot glue gun to add a bead of hot glue on both sides of the top handle bracket and bottom handle bracket. The bead of hot glue will prevent the handle brackets from shifting.

Step 11: Attach the Carry Handle

Mark the Hole Locations
  Center the carry handle horizontally on the outside of the top panel and use a pencil to mark the horizontal position of each screw hole. Measure <span class="reference">&frac34;&rdquo;</span> up from the back edge of the top panel to mark the vertical position of each hole.

  This should line up on the inside with where you glued the filter flange spacers.
Using the carry handle to mark the hole positions on the top panel.
Using the carry handle to mark the hole positions on the top panel.
  ##### Make the Holes

  Using a sharp pointy object, like a <span class="reference">&frac18;&rdquo; drill bit</span>, make holes through both layers of foam board: the top panel and the filter flange spacer. If your hole only goes through one layer of foam board, you may need to use a shorter screw below (or go back and add the second layer of foam board).

  ##### Attach the Handle

  **Inside the box**, line a <span class="reference">#10 &times; 1&rdquo;</span> fender washer up with each hole and then put one of the <span class="reference">&frac34;&rdquo; M4 screws</span> that came with the handle through the washer and both layers of foam board.

  **Outside the box**, place another <span class="reference">#10 &times; 1&rdquo;</span> fender washer over each screw. You should have washers on **both sides** of the foam board. The extra large washers help stabilize the handle and distribute forces over a larger area. Line the handle up with the screws.

  **Inside the box**, use a screwdriver to carefully tighten the screws. Take care not to cross-thread the screws (if you feel resistance, try backing the screw out and adjusting the position) or overtighten them (you don't want to crush the foam board).



  

  

    
    
Attaching the carry handle to the top of the air purifier.

Part 4: Installing the Speed Controller

The fan speed controller in this tutorial does more than just control the fan speed. It actually serves three functions:

  1. It acts as a USB-C PD trigger, requesting 12V from your powerbank, which is what PC fans need to run at full speed.
  2. It acts as a fan speed controller, allowing you to adjust the airflow.
  3. It acts as a 2-port fan hub, allowing you to connect two separate fan cables.

Understanding these individual functions helps when troubleshooting issues or if you need to substitute alternate components.

Step 12: Cut the Holes for the Fan Speed Controller

Mark the Hole Locations

First, we need to mark the locations where the speed knob post and the USB-C port need to pass through the top panel of the box. You can put the fan speed controller in the upper right or left corner of the box (it doesn’t matter which).

To make it easier to mark the locations, pull the speed knob off of the controller (it’s just held on by friction) and pry the top plastic plate off of the speed controller (it’s the side with the label on it). Place the fan speed controller in the upper corner of your choice with the bottom of the controller against the side wall. Use a pencil to mark the locations where the speed knob post and the USB-C port need to pass through the top panel.

Cut the Openings

Carefully cut out the holes using a hobby knife. Start small and frequently test the fit of the knob post and your USB-C cable to avoid accidentally removing too much material. You want a snug fit to minimize air leaks.

Make sure the USB-C cable can fully “click” into the speed controller port when inserted and that the speed knob can turn freely before proceeding.

Dry-fitting the fan speed controller inside the purifier box on a carry style build.
Dry-fitting the fan speed controller inside the purifier box on a carry style build.
Dry-fitting the fan speed controller inside the purifier box on a carry style build.
The holes cut out for the speed knob post and USB-C port.
The holes cut out for the speed knob post and USB-C port.

Step 13: Attach the Fan Speed Controller

Before you glue the speed controller into place:

  1. Test the fit of the speed controller with the fans. Line up one of your fans with the fan hole next to the speed controller to make sure everything fits. If you are using 140mm fans with the rolling luggage style build, you will likely need to pry the top plate off the speed controller (and maybe even remove some of the plastic housing) to get it to fit.

  2. Make sure the speed controller sits flush against the top panel. If there’s excess glue at the seam preventing the controller from sitting flush, use the tip of your hot glue gun to melt the glue and push it out of the way. This is important because the speed knob post needs to stick through the top panel far enough for the speed knob to attach to it.

For a removable bond, apply clear packing tape to the top of the side wall where the speed controller will sit and then use double stick tape to attach the speed controller to the packing tape.

For a more permanent bond, apply hot glue to the back of the controller’s housing and stick it to the inside wall of the box. Make sure the speed knob post and USB-C port are lined up and correctly positioned before the glue cools!

Reattach the Knob

Once you have the speed controller mounted in place, it’s time to reattach the speed knob.

Unfortunately the thickness of the foam board means that the speed knob has less post to “grab” onto. If your speed knob is not secure enough on the post, there are two ways you can help to better secure it:

Option 1: Shorten the Knob

Use a hobby knife to carefully cut away the bottom rim of the plastic knob, shortening it so that it can fit all the way onto the post.

Using a hobby knife to carefully cut away the bottom rim of the speed knob.
Option 2: Use Hot Glue

Put a dab of hot glue inside the speed knob and press partially onto the post, taking care to leave a small amount of space between the edge of the knob and the foam board so it can turn freely.

Part 5: Installing the Fans

Step 14: Plan your Cable Routing

Before mounting the fans, it’s a good idea to lay out all your fans, connect everything together, and plan out how you’re going to route the cables. Attach one splitter cable to each of the speed controller’s two fan connectors, then connect one fan to each of the six splitter cable ends. You want the power draw to be evenly distributed between the speed controller’s two connectors.

You can rotate the fans 90 degrees at a time to use up or give out more slack in the power cables and optimize your cable routing.

If you’re using PST fans, you can daisy chain them instead of using the 1-to-3 splitter cables, but make sure to evenly distribute the load between the speed controller’s two connectors. That means making two daisy chains of three fans each, and connecting one daisy chain to each of the speed controller’s connectors—don’t just put all the fans in one long daisy chain!

Step 15: Mount the Fans & Grills

From outside the box:

  1. Place a #8 × ¾” fender washer over each screw hole on the back of the fan panel.
  2. Place a fan grill over each fan hole, aligning the corners with the washers.
  3. Insert a #8-32 × 2” screw through each screw hole in the foam board from the outside, making sure each one passes through a grill and washer.

Make sure you get the ordering correct! The washers need to sit directly against the foam board in order to protect it from getting crushed when you tighten the screws.

Installing the fan grills with washers correctly positioned underneath the fan grills on a rolling luggage style build.
Installing the fan grills with washers correctly positioned underneath the fan grills on a rolling luggage style build.
Optional: If it's hard to get the screws through the holes, use a ⅛” or ⁵⁄₃₂” drill bit to enlarge them. Simply hold the bit in your fingers and twist it through each hole.
Optional: If it’s hard to get the screws through the holes, use a ⅛” or ⁵⁄₃₂” drill bit to enlarge them. Simply hold the bit in your fingers and twist it through each hole.
Installing the fan grills on a carry style build.

From inside the box:

  1. Place a fan down over each set of screws and secure each fan with 4 #8-32 nuts.

    • Make sure all of your fans are pointing the right way—spinning Arctic logo up—regulatory writing down. You want the blades to push air out of the box (not into it).
    • Use your bare hands to tighten the screws and nuts (no screwdrivers, sockets, or wrenches), and pay close attention while tightening to make sure you don’t crush the foam board!
    • Keep your cables clear of the fans so they don’t accidentally get any trapped underneath.
  2. Route the cables towards the fan hub and connect them to the splitter cables (if using) and the speed controller.
Installing the fans on a carry style build.

Step 16: Secure the Fan Cables

It’s important to secure your fan cables, so that they don’t get sucked into the fan blades during operation. There are lots of ways to do this, but here are a few options:

  • Use the adhesive-backed cable clips (included in the small parts kit).
  • Carefully use small dabs of hot glue to secure any loose cabling. Take care not to touch the cables with the tip of the hot glue gun, as this can easily melt the cabling! Instead, apply a small dab of hot glue at the intended location and press the cable into the hot glue.

Confirm that all of your cabling is secure by gently pulling on it and making sure it cannot reach any of the fan blades.

The fan cables secured using three adhesive cable clips on a carry style build.
The fan cables secured using three adhesive cable clips on a carry style build.

Part 6: Final Assembly

Step 17: Install the Wheels

Position the Wheels

Position the roller wheels on the bottom edge of the box, one on each side. The wheels should stick out from the back—not down from the bottom.

Note that the nuts on the wheels stick out a little ways beyond the edge of the wheel bracket on both sides. Position the wheels ¼” in from the edge of the box to help avoid the nuts catching on things. Make sure the wheel brackets don’t overlap the fan grill washers.

Positioning the wheels on the bottom edge of the air purifier.
Positioning the wheels on the bottom edge of the air purifier.
Make the Screw Holes

Use a pencil to mark the three screw holes on each wheel (one on the back and two on the bottom of the box for each wheel). Then use your sharp pointy object to make the screw holes.

The three screw holes for a wheel marked on the back and bottom of the air purifier.
The three screw holes for a wheel marked on the back and bottom of the air purifier.
Mount the Wheels

Mount the wheels using screws from the outside. Use your remaining two #8-32 × 1” screws for the screw holes on the back of the box and your four low-profile M4 screws for the screw holes on the bottom of the box.

Inside the box, place a #8 × ¾” fender washer over all 6 screws to help distribute the load over the foam board, then use #8-32 nuts for the screws on the back and M4 nuts to secure the screws on the bottom.

The inside of the air purifier showing the wheel mounting points.
The inside of the air purifier showing the wheel mounting points.
The wheel securely installed on the air purifier.
The wheel securely installed on the air purifier.
Apply the Adhesive Rubber Feet

Recall that we had to use special low-profile screws for the bottom of the wheels in order to keep them from scraping the ground. Now we need to apply the adhesive rubber feet to the two front corners of the bottom panel. The rubber feet will raise the front of the box enough that the low-profile screws won’t scrape the ground. They will also help protect the foam board.

Apply one adhesive rubber foot to each of the two front corners of the bottom panel. Use firm pressure when adhering the feet to the bottom panel, but don’t press so hard you crush the foam board.

Step 18: Install the Angled Feet

Take the black plastic angled feet from the small parts kit and line the thick end of each foot up with one of the back corners of the bottom panel. Use a pencil to mark the center of each of the holes.

Marking the holes for one of the angled feet.
Marking the holes for one of the angled feet.
The two screw holes for a foot marked on the bottom of the air purifier.
The two screw holes for a foot marked on the bottom of the air purifier.

Using a sharp pointy object, like a ⅛” drill bit, make holes through both layers of foam board: the bottom panel and the filter flange spacer.

From outside the box, insert a #8-32 × 1” screw through each of the four holes, passing through the angled foot and then the two layers of foam board.

From inside the box, place a #8 × ¾” fender washer over all four of the screws to help distribute the load over the foam board, then use #8-32 nuts to secure all the screws.

Attaching the angled feet on a carry style build.

Step 19: Glue the Filter Flange into Place

Dry Fit

Place the filter flange into the box, letting it rest on the spacers you just glued into place. It should slide in easily. If the fit is tight, trim the edges slightly. A small gap is okay since the hot glue will fill it.

Testing to make sure the filter flange fits on a carry style build before gluing it into place.
Testing to make sure the filter flange fits on a carry style build before gluing it into place.
Glue into Place

Start on any side and work your way around the box. Pull the side of the box and filter flange apart with one hand and apply glue into the gap using your other hand.

Press the filter flange and side of the box together, making sure the filter flange is resting firmly on the supports by also pressing the filter flange firmly into the supports. Continue to apply pressure until the glue has hardened, then move onto the next side.

Avoid pressing down on the unsupported parts of the filter flange while the glue is hardening, or you could end up gluing a bend into the filter flange, which could affect the seal with the filter.

Gluing the filter flange into place on a carry style build.

Once you have glued all 4 sides of the filter flange to the interior walls of the box, check that all of the seams have visible glue. Run a bead of hot glue along any areas that don’t. This ensures the filter flange is securely sealed to the box.

Step 20: Apply the Velcro Patches

Now we’re going to install Velcro patches in each corner of the filter flange and matching patches in each corner of the filter. These patches will securely hold the filter in place, while still allowing for easy removal.

Apply Velcro to the Filter Flange

Cut out four ¾–1” patches of Velcro. We’ll use the rough (hook) side for the filter flange and save the soft (loop) side for the filter.

Place one rough (hook) side patch in each corner of the filter flange. Place the patches as far into the corners as possible—we need to make sure there’s enough room around the inner edge of the filter flange for the weather stripping that we’re going to install in the next step (you’ll need at least ⅜” of space).

Velcro patches to the corners of the filter flange on a carry style build. Note the free space around the inner edge left open for the weather stripping.
Velcro patches to the corners of the filter flange on a carry style build. Note the free space around the inner edge left open for the weather stripping.
Apply Velcro to the Filter

Now we’ll apply the soft (loop) side of the Velcro to the 3M filter.

  1. Look for the airflow arrow on the side of the filter. You want to put the Velcro patches on the side of the filter that the arrow points toward.
  2. Optional: If you want to be able to reuse the Velcro patches when replacing the filter, you can apply clear packing tape to each corner of the filter first. This will allow you to peel up the Velcro patches without the paper coming off with the patch. If you don’t opt to reuse the Velcro patches from the filter, make sure to get the same style of Velcro (i.e. regular vs low-profile industrial strength) so that it sticks properly to the Velcro on the filter flange.
  3. Apply the soft (loop) side patches to the four corners of the cardboard frame of your 3M filter. Make sure to place the patches all the way at the very edge of the filter.
The soft (loop) Velcro patches applied to the corners of the filter.
The soft (loop) Velcro patches applied to the corners of the filter.
Optional: Add Pull Tabs to the Filter for Easy Removal

Adding pull tabs to the filter makes it much easier to remove the filter without damaging the filter or the box. If you purchased the small parts kit, it includes a 1 foot roll of black gaffer tape specifically for making pull tabs.

For each corner of the filter:

  1. Using a strong tape, like duct tape or gaffer tape, cut out a 1” × 2” strip.
  2. Apply the tape to the side of the filter, with the long edge perpendicular to the filter, so that the tape extends out a little more than 1” out past the front of the filter (that’s the side you didn’t put the velcro on).
  3. Fold the extra tape over itself to create the pull tab.
Applying the tape to the corner of the filter. Note the airflow direction on the filter and make sure the tab is sticking out toward the front of the filter.
Applying the tape to the corner of the filter. Note the airflow direction on the filter and make sure the tab is sticking out toward the front of the filter.
Folding the tape over itself to create the pull tab.
Folding the tape over itself to create the pull tab.

Step 21: Apply the Filter Seal

Apply the ⅜” × ³⁄₁₆” foam weather stripping to the top face of the filter flange all the way around the inner edge, taking care not to leave any gaps where the individual pieces come together. This will create an airtight seal with the filter.

Weather stripping applied to the filter flange on a rolling luggage style build.
Weather stripping applied to the filter flange on a rolling luggage style build.
Applying weather stripping to the filter flange on a carry style build.

Step 22: Install the Filter

Place the filter into the air purifier and firmly press each corner of the filter to make sure the Velcro corners are securely attached.

That’s it! You’re done!

You’ve finished building your own portable air purifier. You now have a convenient tool for improving indoor air quality wherever you go. Now go test it out!

Your work has been approved by the supervisor's supervisor!
Your work has been approved by the supervisor’s supervisor!

VII. Operation and Maintenance

How to Use Your Purifier

Plug your air purifier into a compatible USB-C PD power source and use the speed knob to turn on and adjust the fans. The handle (and on the rolling luggage style, the wheels) make it easy to move the air purifier between rooms or take it with you to appointments.

Depending on the fans you select and the speed you run them at, your air purifier should be able to run for many hours on a single charge.

Replacing the Filter

3M filters are rated for up to 3 months of continuous use in a home HVAC system. For portable, intermittent use like this, the filters will last much longer. We recommend replacing the filter when it becomes visibly grey or dirty.

To replace the filter, pull each corner of the filter free using the pull tabs (if you added them).

If you opted to apply clear packing tape underneath the Velcro patches on the filter, you can try to carefully remove the Velcro and then transfer it to the new filter (don’t forget to add packing tape to the new filter first).

If you’re using new Velcro, just make sure to get the same style of Velcro (i.e. regular vs low-profile industrial strength) so that it sticks properly to the Velcro on the filter flange.

Remember to check the airflow arrow on the new filter, ensuring you add the Velcro patches on the side that points into the box.

Add pull tabs (if desired) before installing the new filter.

VIII. Conclusion

This design is a solid starting point, but we encourage you to experiment with different fans, power sources, and design modifications to make it even better.

If you try out different components, make any improvements, have any cool ideas, or otherwise have feedback about this tutorial, please let us know. We’d love to see your build and hear about your experience!

IX. Changelog

  • Version 1.5 — January 1, 2026

    • Added full instructions for the carry style build.
    • Rearranged some of the steps in the tutorial to make the build easier. In particular, we moved the filter flange installation to the end so that you don’t have to work around it during the fan installation process.
    • Added photo gallery section.
    • Rewrote a bunch of the design section: added detailed specs (size, weight, etc.), cost estimates, fan comparisons, and a comparison of the two build styles.
    • Lots of small improvements to the writing and instructions.

  • Version 1.0.4 — December 6, 2025

    • Added a design section at the beginning of the tutorial with a high-level overview of the design.
    • Added some diagrams and a video showing how all of the foam board pieces fit together to make it easier for readers to visualize the build process.

  • Version 1.0.3 — December 1, 2025

    • Added a sticky header with a table of contents for narrow screens and a sidebar table of contents for wider screens to make navigation easier.
    • Added a note about waiting on filter flange installation until after the fans have been installed.

  • Version 1.0.2 — November 2, 2025

    • Updated the 140mm rolling luggage-style template so that there’s slightly more space between the top two rows of fans so that the washers don’t overlap on the back of the fan panel.
    • Added some optional materials to the parts list.
    • Added recommendations for some optional foam board cutting tools.
    • Added some more photos and videos to the tutorial.

  • Version 1.0.1 — September 1, 2025

    • Fixed some typos. Improved styling. Minor content changes to clarify some parts of the tutorial.

  • Version 1.0 — August 27, 2025

    • Initial release