THREAD: 19 Tips for a DIY mask fit test to reduce your risk of #COVID19.
H/t @amandalhu & @__philipn__
What did I miss?
Fit-testing Tip #1: Keep it Simple.
Get a nebulizer (usually $30-40) & some 3M FT-32 Bitrex solution ($24).
Fit-testing Tip #2: Taste the Failure.
Use the nebulizer to spray the bitrex solution (barely visible). Breathe through your mouth. If you taste it, there’s a mask leak.
"It’s not rocket science," as @CorsIAQ likes to say.
Fit-testing Tip #3: Spray at Problem Areas.
I use the nebulizer to spray bitrex fit-testing solution all around the nose bridge, by both cheeks, and under the chin.
You’ll quickly taste a leak.
Fit-testing Tip #4: Go Hoodless.
Do what ya wanna, but for DIY fit testing, the method above works fine w/o the hood.
I bought a hood – overpriced! Plus, the goal is to get as many people as possible fit testing. Many would find them off-putting or feel claustrophobic.
Fit-testing Tip #5: Don’t Test around Maskless People/Animals.
After reinstalling a new filter on my Flo Mask, I did a fit test while my son was having a bath. He started coughing. For a moment, I worried he had COVID.
Put 2&2 together, cranked up the HEPA & gave him juice.
Fit-testing Tip #6: Have a Beverage Handy.
You’re testing for leaks. You will find some. The bitrex tastes horrible, like licking a rubber band. Have some OJ or a soda ready for after you’re done.
Fit-testing Tip #7: Share the Wealth.
Supplies cost $60 total. It takes hardly any fit-testing solution to test, so offer the opportunity to friends, family, or co-workers. You’ll help protect their health & better cocoon yourself from illness too.
I tested all 3 of my favorite N95s: the Aegle flat-fold, 3M Aura, and 3M VFlex. I could pass a fit test with each, some caveats noted later.
Fit-testing Tip #9: Select the Best N95 for YOUR Face.
If you have several masks, test and compare. Go with the winner.
For me, the 3M VFlex held up most robustly. The 3M Aura needs to be readjusted if I talk to much. The Aegle is harder to seal at the nose.
Fit-testing Tip #10: Get your best N95 to fit better.
Although the 3M VFlex most easily & robustly passed fit-testing, I realized I hadn’t been pulling it back far enough under the chin (@jasmith_yorku). I also learned how best to adjust the nose piece to get the best fit.
Fit-testing Tip #11: Elastomeric Masks beat N95s.
I tested 6 elastomeric masks. I hate the word “elastomeric.” It’s alienating.
They’re just non-disposable, reusable masks. Great seal. All outperformed my disposable N95s when testing the limits.
Fit-testing Tip #12: Get your Elastomeric to Fit Better.
Straps can wear out or loosen over time! Filters also need to be reinstalled properly. Use fit testing periodically and when installing new filters to confirm no leaks.
Fit-testing Tip #13: Procedure Masks are a Joke.
Fit tested, fails in <0.5 sec. Air flows to the path of least resistance. Gaps poorly guard against inhaling/exhaling viral-laden aerosols.
Everybody should be using #BetterMasks, paid w/public funds.
Many KN95/KF94 masks are counterfeits, especially on Amazon. Even the city of New Orleans distributed fakes “N95s” last winter. Use fit-testing to check whether a mask is legitimate. thelensnola.org/2022/01/14/cit…
Fit-testing Tip #17: Facial Hair is a COVID Risk.
My disposable N95s start to fail fit-testing after about 2.5 days w/o shaving. My elastos make it about 3.5 days. If you’re clean-shavin, keep it clean.
If you prefer facial hair, use a mask-safe cut, or know the risk.
Fit-testing Tip #18: DBAA.
No, fit-testing is not REQUIRED for masks to “work.”
It’s about improving safety on the margins (5-10%) and especially for the most dangerous prolonged contexts. osha.gov/laws-regs/stan….
FYI, I have no conflicts of interest, such as investing in one of the companies mentioned.
I’m a psychologist just trying to help people understand COVID mitigation tips I didn’t know a year ago so maybe you can reduce your lifetime number of cumulative SARS-CoV-2 infections.
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🌍Want to track COVID transmission accurately worldwide?
This PMC thread walks you through leading dashboards with information more up to date than WHO & EU directories.
🧵 1/
The Pandemic Mitigation Collaborative (PMC) Dashboard provides weekly COVID updates for the U.S., using wastewater surveillance derived case estimation models and analytic forecasting.
Our international directory includes official government dashboards & those developed by citizen scientists.
We exclude countries that have stopped reporting in the past 2-12 months even if on EU or WHO lists. We also exclude low-quality data from opt-in testing programs.
🧵 3/
🔥Biggest uptick since Jan
🔥1 in 167 actively infectious
🔥>2 million weekly infections
🔥700-1,200 resulting excess deaths from weekly infections
Track transmission closer to home w/our new state & international resources 👇
🧵1/6
PMC COVlD Dashboard, Jun 23, 2025 (U.S.)
🔹With >90% probability, we have entered the 11th COVlD wave.
🔹In a room of 50 people, there is already a 1 in 4 chance of an exposure.
🔹We expect nearly 15 million infections in the next month, and rising.
🧵2/6
PMC COVlD Dashboard, Jun 23, 2025 (U.S.)
We continue to expect transmission to break 500,000 daily infections in the U.S. around July 9th.
This is the same prediction as last week, as the forecast was dead on. Yet, there is considerably uncertainty around this timing.
Current transmission (red line) closely tracks that of summer 2023 (yellow line).
We expect to break 500k daily infections between July 9 and the end of July. Our current forecast...
2) PMC COVlD Dashboard, June 16, 2025 (U.S.)
Our current forecast is a bit more aggressive, predicting breaking 500k daily infections by July 9. The 2023 trend suggests end of July.
The 95% confidence interval shows large variation. Note that...
3) PMC COVlD Dashboard, June 16, 2025 (U.S.)
Note that CDC and Biobot both had retroactive corrections to last week's data, meaning the relative "lull" will last a little longer than the uncorrected data suggested. No big news on NB.1.8.1.
1) Here's a quick example of how the federal government is censoring the best scientific research. It's not just cuts to ongoing research.
It's new grant submissions too...
2) In January, I re-submitted a promising Covid/cancer grant to a non-federal funder. Hundreds of pages. Hundreds of hours of work. The best proposal I've submitted as a scientist.
Out of curiosity, I used Sean Mullen's Scan Assist tool to see how many banned words it had...
3) The proposal had 1,750 banned words. No big deal -- they're non-federal.
BUT I had planned to submit a smaller version to NIH this month as a "back up." Impossible!
It's not a matter of using a thesaurus or the find/replace command. The grant is on *Covid*...
CDC wastewater surveillance data show transmission rising. This is our forecast if transmission growth follows typical patterns.
The high & low estimates could be thought of as optimistic & pessimistic scenarios for NB.1.8.1.
2) PMC COVlD Dashboard, June 9, 2025
Notice that current transmission (red line, lower left) tracks closely with two years ago (yellow), slightly below the median (gray), and not far below last year (orange).
Consider each of these trajectories realistic scenarios.
3) PMC COVlD Dashboard, June 9, 2025
All indications are that we are headed into the start of an 11th national wave in the U.S.
We could percolate near the lull point another couple weeks (fingers crossed), but that scenario is becoming less likely.
National COVlD transmission recently fell to its lowest levels since the pre-Delta era.
It's go-time for many who have delayed medical appointments. The situation will likely get much worse in Jul/Aug.
2/ PMC COVlD Dashboard, June 2, 2025 (U.S.)
An estimated 1 in 211 are actively infectious. Most states are "low" or "very low" per CDC.
The situation remains serious even in a relative "lull." >1.5 million weekly estimated infections to result in 600-900 excess deaths.
3/ PMC COVlD Dashboard, June 2, 2025 (U.S.)
By the end of the month, we forecast an increase to 450k daily infections. If NB.1.8.1 takes off, closer to 600k. If overhyped, percolating only slightly higher.