COVID-19 UPDATE: read my new article about N95 masks and coronavirus.
Which mask is the best against pollution? I can’t really answer that for everyone, as our faces have different sizes and shapes. I’ve recently shared results from three large tests, which unfortunately didn’t review many of the consumer masks I’ve used. But I can now tell you exactly which of those popular masks is perfect for me, and maybe we all can learn a bit from my adventure. Here’s my tale.
In my seemingly never-ending quest for the best research on masks, I recently started to correspond with the research team at 3M, and during our conversations they very nicely offered to let me use their machine at their testing lab in Beijing (with no oversight of my results or article). This is the most widely used machine to officially test a mask’s effectiveness on a person’s face, and on a nicely smoggy day (another typically hazardous AQI over 150) I tested nine masks to find out which worked best for my face: three 3M models; Totobobo; Vogmask; Respro Techno; I Can Breathe Honeycomb; Lvdun 绿盾; and a surgical mask.
We performed a quantitative fit test called a on all nine. This test measures exactly what you and I want to know: the ratio of particles larger than 0.3 microns (PM0.3) inside the mask, compared to the particles outside the mask. To perform each test, you punch a hole in each mask and stick one tube in it and another tube outside. This ratio of outside/inside air is called the Fit Factor, and while a proper “pass” would be a Fit Factor over 100, which means an efficiency of 99%, any Fit Factor over 10, which means efficiency of 90%, is also pretty darn good, and a much more achievable target for real world use. This is also called the by OSHA in the USA, and is the target for anyone who must wear a similar mask for their job. For me, my goal for success was a Fit Factor over 10, and super success would be Fit Factor over 100.
The test itself is easy and only takes ten minutes, using a series of positions, each lasting just over one minute: normal breathing; deep breathing; head turning side to side; head up and down; talking; grimacing; bending up and down; and normal breathing. Before each test, to make sure you have a proper seal on the mask, you do a , in my case doing a negative pressure test. This quick check actually is something all of us should perform each and every time we put on our masks: you cup your hands on each side of the mask and breathe in quickly. Your mask should cave in a bit from the negative pressure; if it doesn’t, the seal isn’t tight and you need to adjust.
Enough with the details: what worked best for my face — and what was awful? Without further ado, here’s my Excel graph showing the results, in order of efficiency from best to worst:
The best mask for me
There was only one true winner with a Fit Factor over 100, technically “passing” with efficiency far above 99%: the 3M 9332, a disposable which is certified FFP3 in Europe (N99, essentially). With an incredible Fit Factor result of 240 (99.6% efficiency), this was almost too good, as I found it a bit less easy to breathe than with others. But still, on crazy bad pollution days, I think I’ll be using this one. Besides this model, three others passed the threshold Fit Factor over 10 (90% efficiency): the 3M 9501 at 97%; a Vogmask with 95%, and a 3M 9001V at 92%.
The middle ground
In the middle, with efficiencies in the 80% range, in order were I Can Breathe’s Honeycomb mask at 87%, then the Respro Techno at 85%, followed by my second attempt with the 3M 9001V at 84%, then Tobobobo at 80%.
The worst for me
The worst mask of all was the most popular reusable consumer mask in all of China last year, the Lvdun 绿盾 mask. At only 57% efficiency, this 32 RMB mask was even worse than a 1 RMB surgical mask from my clinic, which did surprisingly not horrible at 63%. Lvdun’s poor results were similar to other poor results from a couple of Chinese consumer group reports that I’ve already discussed in an earlier article. I’m quite astonished that this Lvdun mask is such a good seller in China, and I feel a twinge of anxiety every time I see an adult or child wearing one of these.
My bottom line
Don’t forget that every face is different, and many that one size does not fit all, unfortunately. So my results don’t mean the same mask will work the same for you. Even the same mask can fit differently on the same person on different attempts, as I demonstrated with the 9001V. For me, I found this testing invaluable and I certainly am much more reassured with what I already knew: the 3M brand is by far the most consistent, evidence-based, internationally proven and researched series of masks for me — and maybe for everyone. Their dozens of models have been fit tested millions of times over the last few decades in workers across the world, and I can’t think of any other mask company which even comes close to their reputation and experience.
My everyday mask is now their 9501, which I can grab at any 7-Eleven, only costs 6 RMB, fits flat in my pocket and lasts at least a week. At over 97% effectiveness, on a crazy bad day of PM2.5 concentration of 500 ug/m3, the air inside my mask is around 13 ug/m3 — just within reach of my ideal target of 10. The 3M 9332 would easily get me there. The next time the airpocalypse hits and it starts raining down hellfire, frogs, and PM2.5, I’ll be biking to work as usual, safe and snug inside my mask, wearing my helmet and humming along to Air Supply’s Greatest Hits.
Regarding all of the commercial masks popular especially among expats, I honestly was disappointed in their general results for me, none of which were better than 90% — except for Vogmask. Respro’s Techno filter is officially FFP1 in Europe, which means 78% efficiency, and it actually did better than that on my face. But given how much more expensive it is, I certainly wouldn’t consider this a good value for me at all, especially if a 6 RMB mask can get far better protection. It certainly didn’t help that I found it surprisingly uncomfortable. And in general, 78% protection in China just isn’t good enough, and I don’t think anyone in China should consider a mask certified only FFP1 when so many other masks do better than that. Even on an average Beijing day of 90 ug/m3, an FFP1 mask at best would still give you 20 ug/m3, which is still far above my ideal of 10 and under (equivalent to a healthy AQI under 50).
I was also a bit disappointed with Totobobo, but the result is fairly consistent with a recent test from the China Consumers Association, which only gave it 3.5 out of 5. I find their manufacturer’s suggestions to custom fit their masks with scissors or boiling water quite onerous and certainly at a disadvantage when many other masks are far more effective right out of the package, requiring no customization, at a far cheaper price. The I Can Breathe Honeycomb mask wasn’t so bad, and is very comfortable, but again there are other masks which do far better and are much cheaper. I Can Breathe also has no official certifications, which I feel is another disadvantage. Vogmask was the only one that did very well, but they still don’t have any official ratings nor any large independent tests, so I would consider this my first second choice — but still a second choice. I suppose for now it would be my first choice for my toddler, but I am definitely uncomfortable relying on only one test result from one 8-year old boy. But at least I know it’s far superior for my toddler than Lvdun’s extra small mask, which in previous independent tests performed dangerously ineffective at only 10% efficiency.
I’m starting to think that this entire new industry of pollution masks for consumers should be regulated in order to prevent false health claims, and especially to protect our children from using dangerously ineffective masks. I now find it hard to seriously consider any mask which doesn’t have any official certification (N95 or N99 from USA, FFP2 or FFP3 from Europe, KN95 from China) as well as independent test reviews. I certainly hope that the consumer mask companies continue to nobly rise to the challenges, improve their designs and try to get certifications. In the meantime, I’ll stick with my 3M.
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