Filtrete · Budget build
Filtrete MPR 1900 MERV 13 filters for a DIY box-fan purifier (4-pack)
The US EPA's do-it-yourself air cleaner: a MERV 13 filter taped to a 20-inch box fan.
Four filters make a Corsi-Rosenthal box, which cleans faster.
- MERV 13, the rating EPA suggests
- 4 filters: enough for a Corsi-Rosenthal box
$87.99at walmart.com · 4 filters · Oct 2026
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Filtrete MPR 1900 MERV 13 filters for a DIY box-fan purifier (4-pack) at a glance
- Rating
- MERV 13 (Filtrete MPR 1900)
- Size
- 20 × 20 × 1 in nominal (about 19.7 × 19.7 × 0.8 in)
- Pack
- 4 filters
- Fan you'll need
- A 20-inch box fan, UL- or ETL-listed, 2012 or newer (EPA)
Our take
When smog arrives and purifiers sell out, a box fan and a furnace filter work. The US EPA's simplest design straps one MERV 13 filter to the back of a 20-inch box fan. Four filters taped into a cube with the fan on top, the Corsi-Rosenthal box, clean faster still.
It's loud and not pretty, and it has no AHAM rating. But for a big room on a small budget, it's about the cheapest clean air you can buy.
It has no AHAM rating, so the room-size filter leaves it out. Replace the filters when they turn grey.
What's good
- Cheap and quick to set up
- Based on the EPA's tested DIY design
What's not
- No verified CADR
- Louder and bulkier than a real purifier
Good for
- A big room or a classroom on a tight budget
- A stopgap during a smog emergency
Skip it if
- You want it quiet: a box fan on high is loud
How it compares
Every air purifier in the shop.
| Product | Best for | Smoke CADR | Room size | Price |
|---|---|---|---|---|
| Levoit Core 300S | Smart bedroom | 141 cfm | 20 m² | $149.99 |
| Levoit Core 300 | Budget bedroom | 143 cfm | 21 m² | $89.99 |
| Levoit Vital 100S | Pet-friendly bedroom | 143 cfm | 21 m² | $119.99 |
| Coway Airmega 150 | Small & quiet | 153 cfm | 22 m² | $189.99 |
| Levoit Core 400S | Shows PM2.5 | 231 cfm | 33 m² | $189.99 |
| Winix C545 | Everyday pick | 232 cfm | 33 m² | $209.99 |
| Coway Airmega AP-1512HH Mighty | Best overall | 233 cfm | 34 m² | $239.99 |
| Coway Airmega AP-1512HHS (Mighty with Wi-Fi) | Smart Mighty | 233 cfm | 34 m² | $299.99 |
| Coway Airmega 200M | Mighty's twin | 233 cfm | 34 m² | $229.99 |
| Levoit Vital 200S | Pet homes | 250 cfm | 36 m² | $169.99 |
| Honeywell HPA300 | No-frills power | 300 cfm | 43 m² | $269.95 |
| Coway Airmega 400 | Big rooms | 376 cfm | 54 m² | $649.00 |
| Levoit Core 600S | Large rooms | 391 cfm | 56 m² | $299.99 |
| Blueair Blue Pure 211i Max | Most clean air | 435 cfm | 63 m² | $349.99 |
| Filtrete MPR 1900 MERV 13 filters for a DIY box-fan purifier (4-pack) (this one) | Budget build | — | — | $87.99 |
In our buying guides
Questions about the MPR 1900 MERV 13 filters for a DIY box-fan purifier (4-pack)
- How do I build a box-fan air purifier?
- EPA's simplest design puts a 20 × 20 in MERV 13 filter on the intake side of a 20-inch box fan, with the airflow arrow pointing at the fan. A cardboard shroud and more filters improve it; four filters plus a base make a Corsi-Rosenthal box.
- Is a DIY box-fan purifier safe?
- Use a UL- or ETL-listed fan from 2012 or newer, as EPA advises, and keep its motor vents clear.
How we judge. We haven't tested the MPR 1900 MERV 13 filters for a DIY box-fan purifier (4-pack) in a lab of our own. The figures come from independent ratings (AHAM, Energy Star, NIOSH, the ASPCA) or the maker, and the verdict is ours, from those figures. No brand pays to be listed. Last checked Oct 30, 2026.
Filtrete MPR 1900 MERV 13 filters for a DIY box-fan purifier (4-pack)
$87.99 list price