Why do some masks in ads have a black round thing like A camera lens

[raccoon]

On Them?

[janterry]

1. edited because I was wrong

Last edited Thu May 21, 2020, 08:42 AM - Edit history (1)

check below!

[ProfessorGAC]

3. Probably The Actual Filter

Meant to reduce pressure drop, and still capture microscopic particles.

[jberryhill]

6. .

[ProfessorGAC]

8. Wore My Share Of Chemical Respirators

Not that many particulate masks, though.
On a chemical respirator, the air flow is obvious.
And, when putting on, folks are trained to self-check fit.
Index card over the cartridges, and inhale. Hand over outlet valve, exhale.
I wasn't in high dust areas very often. Only a half dozen times? And I don't recall anything other than a regular dust mask like drywallers wear.
So, I figured my answer was right, but wasn't sure.

[jberryhill]

10. There's all sorts of nonsense being sold on the internet

So what, in particular, might be the question is a jump ball.

[Buckeye_Democrat]

4. Probably a one-way exhaust valve.

Exhaled breath can escape more easily that way, so it's not very conscientious to other people if they're worn in public.

I have those types of masks, but use a neck gaiter to cover the valves.

[jberryhill]

7. I dunno

Given that the pores in fabric are orders of magnitude larger than the virus, and since the goal is really to capture humidity, the interrupted airway path introduced by the check valve is still better than nothing.

[jberryhill]

5. It's not the filter

It is a check valve.

[Buckeye_Democrat]

9. Like this?