Thread by @JenniferKShea

To the experts insisting “N95s are useless if not fit-tested”

Have you ever tried to fit test a “well-fit surgical mask” or “3 layered well-fit cloth mask”?

TLDR they are inferior.

A brief case series and 🧵

1/15

There are two type of fit tests, 1) quantitative fit testing - a portacount machine measures the concentration of aerosol outside the mask versus inside the mask and 2) qualitative fit testing - a potent bitter or sweet aerosolized solution is inhaled under a hood

2/15

I underwent quantitative fit testing on a surgical mask, suboptimally fit KN95 and well fit CN99 (FFP3). The results were intuitive. The surgical mask, while still offering some protection, performed the worst.

3/15

https://twitter.com/JenniferKShea/status/1388555055125643267

Not everyone has access to formal quantitative fit testing. Aside from performing a self-seal check, can you DIY your fit test?

Yes!

phc.amedd.army.mil/PHC%20Resource…

4/15

https://twitter.com/__philipn__/status/1419938176521539585

A basic nebulizer + 3M bitrex solution + plastic bag = DIY qualitative fit test.

5/15

Inhaling the nebulized bitter solution without a mask is almost immediately overpowering for most people (some people aren’t able to taste the standard bitrex solution, thus always important to test with no mask first)

6/15

I repeated the experiment with two ASTM 3 surgical masks. The bitter taste hit my taste buds within 5-10 seconds. Clearly suboptimal protection for aerosols.

Note- ASTM std is primarily for high velocity liquid spray protection & was NOT designed to protect inhalation

7/15

I “passed” my brief DIY experiment using CAN99 vitacore, CAN95 vitacore, 3M Vflex, ASTM 3 surgical mask with fix-the-mask brace to improve the seal, envomask N95, and DenTec P100 Elastomeric

8/15

My next family participant was tested on a vitacore ASTM3 surgical mask and the 3M vflex.

His tastebuds remained bitter-free with both masks. The surgical mask happened to fit his face very well with a tight seal all around.

3M Vflex sealed well and was more comfortable

9/15

Next family participant only tested his mask of choice, the 3M Vflex respirator- he remained bitter-taste free after a minute of inhaling the concentrated solution.

10/15

My next participant was unable to taste the bitrex, thus couldn’t complete the experiment. However, the CAN95 vitacore ear loop mask (with silicone toggles to tighten the loops) appeared to seal her face well.

11/15

My final participant was a good sport and tested a few masks. First up was a vitacore CAN95 ear loop mask with nose bridge pre-flattened and silicone toggles on the loops to tighten the fit. This appeared to fit her face well.

It successfully blocked the bitrex taste.

12/15

Her next mask was a high quality 3 layer cloth mask, which appeared to fit her face well.

Unfortunately, she failed within 10-15 seconds of inhaling the bitrex.

13/15

Finally, she tested an ASTM3 surgical mask.

Not surprisingly, given the visible cheek gaps, she failed with this one as well.

14/15

Unless you’ve inhaled bitrex under a DIY bag hood, don’t assume your cloth mask or surgical mask is offering superior protection. It will always be better than no mask, but we need to choose #BetterMasks and #BestMasks to end this pandemic

#N95s4All #RespiratorsNow

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