A well-fitting elastomeric respirator is something everyone should have on hand for emergencies. [1] Primarily for infection prevention, since a future pandemic could be much worse than covid, though they're also useful for smoke. There are a lot of options, though, and which one is best for you depends on the size and shape of your particular face. To help people figure out what they should get, I'll be hosting a fitting session in Somerville on 2025-05-22; write jeff@jefftk.com for location. Drop in any time between 7:30 and 9:30pm.

If you have a beard I recommend shaving before you come: in my testing I couldn't get a full seal with anything more than a short stubble.

I'll have the following masks available for testing:

• ElastoMaskPro: Small ($30), Large ($30)

• Envo Pro: Standard ($41)

• 3M 6200 P100: Small ($17 + filters), Medium ($16 + filters), Large ($19 + filters)

• 3M SecureClick with Speaking Diaphragm: Small ($56), Medium ($61), Large ($59)

• GVS Elipse P100: Small-Medium ($35), Medium-Large ($41)

• Flo Mask Pro: Low-Medium ($90), Medium-High ($90)

• Flo Mask Kids: Age 4-12 ($50)

Some of these are valved masks, while others filter your exhalation ("source control"). There are advantages to both:

• Valved masks are easier to breathe in, are less likely to fog glasses and generally build up less condensation, and reduce your CO2 intake.

• Unvalved masks reduce your chance of getting others sick. If a mask reduces risk by two logs, both people wearing unvalved masks reduces risk by four.

For some of the respirators you can determine if you have a good seal by closing the valve and seeing if you can still breathe; the 3M SecureClick even has a button for this. For the others I'll have a qualitative fit test setup (hood, sweet and bitter test solution, nebulizer; video) if you'd like to see how well the filtering is working.

Afterwards I'm happy to lend out the collection of respirators and the fit test kit to others who would like to hold their own fitting sessions.

[1] Some back-of-the-envelope math: let's very conservatively guess that:

• A really bad pandemic has at least a 1% chance of happening in the next ten years.
• If one does happen, having a well-fitting high-filtration respirator would have a 1% chance of making the difference between you surviving and not.
• Surviving is worth $7.5M to you.

Then spending $50 on one to set aside now is worth ~$700 in expectation. Plus some benefit from getting to use it in less severe scenarios, and some quality-of-life benefit in a range of scenarios.