Beat The Smoke Without N95

DIY Filter

Update: With one of these in my room, the PM2.5 stayed at zero even when the outdoor PM2.5 was over 800!


Hoarding N95 masks and other medical supplies during covid is irresponsible and unhelpful. I will show you a better alternative.

I have severe asthma. As such, fire season in California poses a real threat even without the additional risk of a respiratory pandemic. Many of the comorbidity factors from covid-19 are related to respiratory issues, and while asthma is not one of those factors, we don’t know the impact wildfires will have. As such, I wanted to make sure to prepare early since all the N95 masks are needed for coronavirus.

One expert I interviewed let me know that in fact unless you are shaving every day and wearing a professionally fitted mask, N95 is actually not significantly more helpful than simple fabric face wraps. Many recent studies and academic articles have corroborated this.

N95 masks are the ones that can filter both smoke and coronavirus, if they are professionally fitted on someone who is shaving daily. Therefore they are in extremely high demand by medical professionals who need them. I would not buy them for that reason. Also, I still have a dozen or so left over from burning man last year. (N95 also filters playa dust.) Sadly though I tried, I was not able to donate these because the box was opened. If you have unopened N95 masks, please donate them to medical professionals who actually need them, rather than hoarding life-saving supplies.

I have spent several years together with friends exploring the best ways to filter the indoor air quality during fire season. According to NASA research, one of the best things you can do is to have the right kind of indoor plants. Unfortunately while this filters many harmful chemicals, in my experience it does not seem to be effective against smoke. I am conducting an extended research project to look at this question and I will be reporting back soon. I have tried many different kinds of air filters, and landed on a very solid and excellent setup.


($8 ea) 20×20″ MERV 11 Filter

($20) 20″ Box Fan

$28 Total

Houses and Faces

An N95 mask is certified on a scale called NIOSH. N95 mask certification actually has nothing to do with viruses. It is a scale for filtering particulates which do not contain oil; this includes viruses as well as smoke particles. N95 masks are also certified for biocompatibility since they are touching the face. There are many other factors that go into the N95 mask certification.

NIOSH Ratings

For the purposes of this post, all that really matters is filtering smoke. So when we look for a house filter to fit the need, we don’t necessarily care if it’s ok to wear it on your face or how resistant it is to oils.

House filters are rated on a completely different scale called MERV. MERV 11 and up are rated for smoke.These filters cost less than ten dollars and last months. MERV filters are not certified for biocompatibility since they are not designed to touch your skin. Do not use house filters on your face. They can contain dangerous materials which are not safe for your face. Cutting house filters into face masks can release fiberglass and other dangerous materials which can hurt you.

MERV Ratings

There are any number of expensive air filter products you can buy which run up into the hundreds of dollars. I am going to show you how to accomplish the same quality air filtration for just $30.

One common size for MERV 11 filters is 20″ x 20″. This is the same size as the generic $20 box fans you can find at any department store from Walmart to Home Depot.

It’s a simple matter of using a few pieces of tape to attach the filter to the back of the fan. Now you have one of the highest quality air filters you can get for just $30; certified for both smoke and for viruses.


For just $30, you have essentially the highest quality air filter possible which will last for years depending on your situation. In my case, one or two MERV filters lasts me the full fire season.

DIY Filter

Breathe easy!