How Good are N95 Masks For Pollution?

I get a lot of questions from expats in Beijing, especially bikers and people walking to work, who wonder whether any type of mask is helpful. I also bike to work so I was curious as well. We’ve talked a lot about N95 masks for the flu, but how well do they work for pollution?

I previously discussed a fascinating small study done here in Beijing, with subjects walking along second ring road wearing masks. They had researched common masks and decided on the 3M company’s 8812 mask as the best for the study, which is N95 rated and also has an exhalation valve to help breathing and prevent fogging of eyeglasses. They compared this to other masks and decided that the 8812 was the best option for this test due to effectiveness, price and comfort. Here again is the graph:



The “N95” literally means that 95% of fine particles are blocked by this mask. Note that the 8812’s effectiveness in blocking particles over PM0.5 was over 96%; note also that this was far better than all 4 tested cycling masks, as well as the simple cloth masks we now see all over Beijing. Unfortunately, they did not specify which brand of cycling mask was tested. Also of note is that the simple cloth masks that are popular now in the winter (kouzhao 口罩) are minimally effective against fine particulates, only blocking 28%.

The 3M company is highly regarded as making professional-grade safety products, and they have a big line of dust respirators geared mostly for construction teams. I couldn’t find this 8812 locally, so I used Taobao and had a few boxes delivered from southern China.

My Routine

I bike to work and back, so in the mornings and evenings I will check the website iphone.bjair.info to see the hourly-updated air quality at the US Embassy, only a couple hundred meters from me and therefore highly relevant. If the AQI is high (anything over 200) I will definitely use the mask on the way to and from work. Since it is at least 95% effective, that means that the most air-toxic days with AQI of 500 would bring my exposure down to 0.05% of that, or 25, which is considered safe by the WHO. So, indeed, these masks can work very well against fine particulates, the most serious pollutant. Yes, I get some looks but that’s a small price to pay for breathing better. At least in the winter it is less noticeable as most everyone is wearing some type of face mask (kouzhao) as a warmer. Today, I just bought a simple black kouzhao for 3RMB on the street and will try to wear it over the N95.

The Bottom Line

I’m very comfortable with the 8812’s effectiveness against air pollution. As for comfort, the yellow straps are fairly comfortable and the foam-lined mask is very comfortable. Plus, my eyeglasses do not fog up, a big problem with the regular N95 masks I previously used. And as for aesthetics, I do wish it were a bit snazzy and may get self-conscious in the spring and summer, but again, the health benefits far outweigh any loss of coolness.

What about other pollutants? Yes, it’s true, there are vapors, ozone, nitric oxides and others which may not be blocked by this mask. But fine particulates have the most evidence regarding long-term and short-term health risks, and are considered the most serious risk by the WHO.

What does everyone think?

I’d be very interested in having people write comments below as to what, if anything, they use, and when they decide to use it.




Follow me on:
Twitter @RichardStCyrMD
Facebook @BainbridgeBabaDoc
Photography: richardsaintcyr.com

8 thoughts on “How Good are N95 Masks For Pollution?”

  1. Oil-based is for use with volatile organics VOC's , i.e. paint mist/fumes, etc. you want the non-oil based masks. As much as I like riding and exercising I can't imagine doing it when the air is bad. I would suggest getting regular tests for lung capacity as a minimum, spherometers are cheap and can be done by yourself.

    1. The overall use of spirometry for lung function won’t really help people make better health decisions. Sure, it’d be interesting to see how much worse your lungs may be after a bike ride, especially an asthmatic. But with or without testing, the issue of air quality is the same. I think on the worst days, optional weekend bike rides even with a mask probably aren’t a good idea. But bike commuters don’t have that luxury…That 3M 8511 looks the same as the 8812; where did you buy it, and how much?

  2. I use the 3M 8511 mask. Comfortable and the flexible M-clip on the top allows for a close fit around the bridge of the nose. The exhalation valve is a must-have. I wear it running and walking in the morning; after about 4-6 hours of usage the filter looks brown; i cut them open each time and looking at the stuff they stop from going into your lungs is amazing!

    I'm curious how 3M has separate classifications for "non-oil based" and "oil based" pollutants — the 8511 is for non-oil pollutants.

    I presume car exhaust is an "oil based" pollutant and therefore it would be better to get one that has the oli based protection?

  3. I use the Respro Techno mask when I bike around town. If the sky looks particularly dusty I'll do a check on the Beijing API pollution index and if it's above 100 then I'll wear it when I'm walking around too.

  4. You should also ensure that the seal around the mask is intact. Hospitals use a test to ensure there are no leaks. Put your mask on and find something highly aromatic (they use vanilla) and put it near your face. If you can smell it, then you have a leak. Certain masks may not be shaped to your face or head. The problem area is often the nose piece, which does not fit snugly enough. Wearing an N95 while cycling would be uncomfortable due to the reduction of air you'll experience, but if I was in Beijing I'd use one. There are canister-style (canister is disposable) masks as well, also certified for N95. They are bulkier but may fit better.

  5. You may also be interested in totobobo mask, a transparent mask which is easier to ensure fit. I use it last time when cycling in Vietnam. I can see that it helps to block a lot of dirt from entering my lung. The best part is that the mask is reusable, and the filters are very cheap.

Leave a Reply