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Do Any Anti-Pollution Masks Work? Look at the Research

Thomas Talhelm, Asst. Prof Behavioral Science, University of Chicago Booth School of Business; Smart Air Founder. Disclaimer: I’m not an expert in air pollution. I’m a psychologist, but I got interested in air purifiers and masks when I was living in Beijing and the pollution levels went off the charts.

Has there been reputable research on the effectiveness of anti-pollution masks? Which ones work? Which ones don’t? Is it recommended to wear these or is this unnecessary?

Note: I’m talking specifically about anti-pollution masks for traffic, where one would be exposed to, most notably, fine particulate matter, NOx, O3, and hydrocarbons.

The research on whether masks protect against particulate is clear. To explain it, I think it’s easier if I break it down into three smaller questions:

1. Can masks get the really small particles?

Researchers tested air masks by running a diesel generator (to mimic car exhaust) and piping the exhaust through different masks. They used a particle counter to see how many particles made it through the mask.
First they tried a simple cotton handkerchief. Sometimes I see bikers in China wearing these.
Not great, 28% of particles blocked.
Next they tried a cheap surgical mask.

Surprisingly good! (Fit tests generally show lower results–see below–but still a lot higher than most people’s intuition.)
Next they tried several bike masks.

Most were around 80%.
Then they tried several cheap 3M masks.

All over 95%. Pretty good!
Conclusion: masks capture even very small particles.

2. Do they actually work when you wear them?

This question is tougher to answer because you have to measure it while you’re actually wearing it. For that, you need a really expensive fit test machine. Fortunately, I begged and begged 3M until they let me go use the machine in their Beijing lab:
The blue tube is sampling air outside the mask. The white tube is sampling air from inside the mask.
An American doctor in Beijing Richard Saint Cyr also did this test. His results were similar to mine, although he tested more masks, so I’ll present his data:


Again the cheap 3M masks were blocking well over 90% of particles.  Also note the surgical mask here blocked about 60% of particles, which is not quite the 80% from before, but still more than most people would guess.

I enjoy seeing what happens when you overlay price (in Yuan) and effectiveness:


I use the 3M 9332 now, rather than the Respro masks I used to use.

Of course, these tests are based on Dr. Saint Cyr’s face, so they won’t necessarily generalize to everyone. However, I have three data points that found almost identical results: his face, my face, and my collaborator Anna’s face:


Conclusion: masks block small particles while we’re wearing them.

3. Is there a documented health benefit of wearing a mask?

This is probably the hardest question to answer. I know of only one study that has tested it directly. The short answer is: it appears to lower blood pressure and regulate heart rate for people walking in Beijing. I describe that study in more detail here:

Is there a medically proven advantage to wearing a pollution mask when cycling?

Disclaimer: This doesn’t address gas pollutants like NO2 and O3. That said, the evidence for the capturing of particulate is strong. When I bike in Beijing without a mask, my airways constrict, and I feel like I have asthma. When I wear a mask, I can breathe fine.

Anyone who watches movies and TV series would identify three kinds of masks/respirators.

— The simple flat mask, also known as a surgical mask that doctors wear.



— The more sophisticated dust and particulate mask known as a respirator worn by traffic policemen at crossings and tourists


— Those post apocalyptic gas mask or respirator made famous by the TV series Breaking Bad.


Each type has a particular application:

Surgical mask acts as a simple filter against particulate matter, the respirator usually offers better protection from suspended particulate matter while the gas mask protects against chemical fumes depending on the kind of filter they are fitted with.Now the question is what type works best as an anti pollution mask? According to an article in Quartz, urban Chinese are spending a lot of money on anti pollution masks that are practically useless. Most buy simple surgical masks that do not filter PM2.5 particulate matter, the most harmful of the lot. Another study in India by the IIS found that most Indian either use the wrong types of masks or do not know how to use them in the right way.

All masks are helpful to protect from air pollution, smog and smoke pollution, chemical pollution, etc.

Cambridge N99 Masks

Cambridge Masks are N99 Masks that use military grade filtration technology to filter out nearly 100% of particulate pollution, gases, as well as bacteria and viruses in a fashion friendly mask suitable for the whole family. Cambridge Mask technology was developed by UK Ministry of Defense for protection against chemical, nuclear and biological hazards. We call this the British Pollution Solution. Our pollution masks help protect against gas based pollution, such as smells, benzene and formaldehyde, particle pollution such as PM2.5, pollen or smoke and pathogens such as viruses and bacteria. Ideal for cyclists, people in at risk groups for respiratory disease or anyone living in urban environments with high air pollution levels.

Why are anti-pollution masks necessary in India?

Air Pollution in India has come to an alarming stage. According to WHO, India has crossed China in being the most polluted. Several reports published in 2016 state that 12 of the Indian cities are listed in the “Top 20 World’s Most Polluted Cities”.

The outdoor air contains several pollutants that can cause serious health hazards. The most dangerous pollutants in the air are dust, PM10, PM2.5, PM0.3, virus, bacteria and gas pollution. These pollutants can cause respiratory diseases, cardiac diseases, COPD and lung cancer.

In extreme pollution condition of India, it is best advisable to wear anti-pollution masks that are N99 certified.

Why choose Cambridge N99 Masks?

— These masks are N99 tested and have been treated with silver, which allows the mask to block and kill 99.77% of micro particles such as airborne bacteria.

— N99 Masks have filters that can block 99.6% of all viruses.

— The military carbon layer of the mask fully absorbs pollutants such as liquid particles and gases.

Find Pollution Air Masks