Options and sources
CR box air filters are powerful, inexpensive, and some are super quiet. And they can go in a classroom or business or home right away, adding filtration capacity ASAP, even if your school district or landlord or HVAC system is not ready to provide sufficient ventilation to make your indoor air safe.
Our favorites we recommend and have experience with are the CleanAirKits.com Tower of Power, the Owl Air, the traditional CR box using a box fan, and the Elfstrom single fan filter. All of these options can be DIY’d, and some can also be purchased if you are short on time to commit to doing your own build.
Easy mode – CR boxes you can buy
Owl Air
There are currently stalled efforts to develop the Owl Air LLC, with a goal of making it available for sale. Interest in purchasing might revive the effort. If you’d rather buy an Owl Air than make one, please reach out to info@safeairoregon.org so that we can pass along interest to the Owl Air LLC folks.
Tower of Power
Two options are available from CleanAirKits.com:
Option 1: STEM Kit
Total price: $270
- Blending easy mode of purchasing with the fun of doing a DIY build
- The STEM kit includes parts for assembling the fans into a sturdier, and more easily reusable, frame than our current DIY build — the cost for all the parts you need to build the frame is ~$225 ($209 + shipping)
- 2 3M 20×30 MERV 13 filters need to be bought separately – $45 for 2 filters at Amazon or Lowes, or stock up and buy 4 for $72 at Lowes.com
- Total for one STEM Kit version: $270
- Purchase the frame parts here selecting “DIY STEM kit” and the filters here
Option 2: Pre-assembled with filters
Total price: $340 — not currently available
- Super easy mode! This is fully ready to go out of the box. Cost is $289 + ~$55 for shipping.
- Total for pre-assembled version: ~$340
- Purchase both the fame and filters all ready to go here
Save money mode – CR boxes you can build
DIY Owl Air CR box
Total price: ~$160 – $175
Warning: This build is dependent on the Honeywell HF-910 fan, but the HF-910 seems to go in and out of being in stock or not. Some of our members have been told that it goes in and out of availability because it is a seasonal item, while others have been told that Honeywell is discontinuing this fan. Fingers crossed it remains available!
| Tools and materials needed | Recommended sources + typical price |
| Honeywell HF-910 + the box the fan comes in | When in stock, Staples & Walmart have given free shipping – $57 |
| 4 MERV 13 furnace filters Size: Either get 20” x 20”, 20” x 25” or 20” x 30” filters We are also experimenting with a build that uses 24″ x 30″ filters We may recommend this size in the future | 3M Filtrete Amazon Get a 4-pack of 20×20 or 20×25: $92 ($23 each) or Get 2 2-packs of 20×30: $90 or Build three CR boxes with 2 6-packs of 20×20: $250 ($20.85 ea/$83 per 4 filters) Lowes.com **Best deal ($18.40/filter) + delivery is free & quick Get 4 filters (any size): $74 (Lowes discount off of $92 if you buy 4 filters at once: 20%) |
| Tape + covering materials Recommendation: Gaffer’s tape in two sizes (2” and 4”) If you prefer, you can also use duct tape, or duct tape and contact paper But we’ve found Gaffer’s tape to be the easiest to work with | Amazon Get 1 roll of 2-inch black Gaffer’s tape: $20 You can also bring the cost of a roll down to $9 with 4- and 6-packs And Get a 2 pack of 4-inch white Gaffer’s tape: $21 A 2-pack will cover multiple Owl Air box tops |
| Weather stripping & glue (optional) | 3/16” weather stripping ~ $3 |
| Scissors, measuring tape | N/A |
DIY Tower of Power CR box
Total price: ~$175 – $250
| Tools and materials needed | Recommended sources + typical price |
| 10 Arctic P14 PWM PST PC fans Note: The Arctic P14 and the Arctic P14 PWM PST are two different versions of this fan The PWM PST option is ready to plug together and has worked well | Amazon 2 5-packs – $50 per 5-pack – $100 total |
| 2 MERV 13 furnace filters Size: 20” x 30” filters | 3M Filtrete Amazon 1 2-packs of 20×30: $45 ($22.50 ea) Lowes.com 4 20×30 filters: $74 (Lowes discount off of $92 if you buy 4 filters at once: 20%) |
| Tape Recommendation: 2” Gaffer’s tape You can also use duct tape, but we’ve found Gaffer’s tape to be the easiest to work with | Amazon 1 roll of 2-inch black Gaffer’s tape: $20 (You can bring the cost of a roll down to $9 with 4- and 6-packs) |
| Thick foam posterboard | Michael’s 2 – 20×30″ Core Foam Boards – $8 ea – $16 total If making 2 CR boxes, get 3 – $24 total |
| Power adaptors | Amazon Get DC power supply Chanzon 12V 2A 24W Class 2 Power Supply AC DC Switching Adapter – $15 and Get fan power adapter cable CRJ Female DC Power Supply Plug to PC 3/4-Pin Fan Power Adapter Cable $5.50 for 1 2-pack for $7.99 – if making 2 CR boxes |
| Hardware & screening (or fan grilles) *Ask if we have extra hardware & screening to give to your build | Get hardware: 40 45mm M4 bolts, washers, nuts – $34 for 100 of each (covers 2.5 boxes) and Get screening: Plastic chicken wire mesh – $15 (covers multiple boxes) or Alternative to screening: 10 PC fan grills – $12 |
| Box cutter, glue, template | Borrow our template or get large thick paper to DIY |
Traditional DIY CR box with box fan
Total price: ~$100 – $130
| Tools and materials needed | Recommended sources + typical price |
| 20 inch box fan + keep the box for making the optional but flow-enhancing shroud | Lasko or Utilitech – $30 |
| 4 MERV 13 furnace filters Size: Either get 20” x 20”, 20” x 25” or 20” x 30” filters | 3M Filtrete Lowes.com 4 filters (any size): $74 (Lowes discount off of $92 if you buy 4 filters at once: 20%) |
| Tape + covering materials Recommendation: Gaffer’s and duct tape If you prefer, you can use just duct tape, or duct tape and contact paper | Amazon 1 roll of 2-inch Gaffer’s tape: $20 You can bring the cost of a roll down to $9 with 4- and 6-packs 2 pack of 4-inch white Gaffer’s tape: $21 These 2 packs will cover multiple shrouds 1 roll of duct tape: $9 |
Elfstrom single filter fan CR box / SAFE Box
Total price: ~$60 – $80
| Tools and materials needed | Recommended sources + typical price |
| 20 inch box fan + you need the box | Lasko or Utilitech – $30 |
| 1 20×20” MERV 13 furnace filter | 3M Filtrete – $23 each at Amazon or Lowes.com Or get 4 filters for making 4 CR boxes – $74 from Lowes.com – best deal at $18.50/filter (Lowes discount off of $92 if you buy 4 filters at once: 20%) |
| Tape + covering materials Recommendation: Gaffer’s and duct tape | Amazon 2 pack of 4-inch white Gaffer’s tape: $21 These 2 packs will cover multiple Elfstrom boxes 1 roll of duct tape: $9 |