As cities like Delhi, Beijing and Manila face toxic levels of air pollution, people are rushing to find effective pollution masks, particularly kid’s masks.
But there’s a problem. Children’s faces are different from adults’. Add to that, children are constantly growing, meaning that the mask that fit last year might not fit this year.
Kid’s Mask Fit Test
To help worried parents, we ran open-source fit tests of with two children in Mumbai. We tested the small size of the Honeywell H950V mask, which is designed for kids.
Two young volunteers helped test the kid’s masks: Pallavi (8 years old) and Vijay (10 years old).
How the kid’s mask fit test works
We know that masks are highly effective at capturing PM2.5 particles, even down to .007 microns.
But showing that masks filter particles isn’t enough. We need to know whether they work when children are actually wearing them. This is a pressing question because most masks are made (and tested) on adults, who have larger faces.
The fit test measures effectiveness while a real person is wearing the mask by using the white tube to sample air inside the mask. Meanwhile, the blue tube is sampling air just outside the mask.
The TSI PortaCount detects particles down to .01 microns—far smaller than the oft-mentioned 2.5 microns. Then the machine uses this to estimate the percentage of particles going through the mask (as opposed to leaking in around the sides).
Effectiveness varied 40% between the two children. This suggests that it’s important to find the best-fitting mask for each child.
In our adult tests, pollution masks averaged 95.4% fit effectiveness. Fit effectiveness was lower on both children.
Help fitting the kid’s masks
To test whether instructing the children carefully on how to put on the mask, we ran each test again after giving each child careful help fitting the mask.
After careful fitting, Vijay’s fit score increased to 94%. However, Pallavi’s score remained at 50%.
Thus, careful fitting seemed to help only a little bit. The low score for Pallavi may mean she needs a smaller mask.
Bottom line: Compared to wearing no mask, both children breathed significantly less pollution with the Honeywell mask. However, the 40% variation in effectiveness suggests it is worthwhile to try several masks to find a model that fits your child.
Help your child do a kid’s mask fit test
Don’t have access to a $10,000 TSI mask fit-testing machine? You can follow the simple steps of a poor man’s fit test for free with your child.
Three More Things You Should Know About Masks
We have more data! Read more about the results of:
- Open-data fit tests of 18 masks available in India.
- How long do masks last? Just one day? We ran a longevity test of new masks versus masks that have been used for several weeks.
- Do masks capture really tiny particles? Is there any documented evidence that masks have real health benefits? Here’s what the empirical data on masks says.
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Thomas is an Associate Professor of Behavior Science at the University of Chicago Booth School of Business and the founder of, a social enterprise to help people in China breathe clean air without shelling out thousands of dollars for expensive purifiers.