Lately the tree pollen has been really thick in the air. There's a fine yellow powder on every surface. When I breathe it in, especially when mowing the lawn, I start coughing and my throat feels like it's about to close up. So I am wearing a respirator, but it's not working.

It is fitting tightly against my forehead and temples and jawbone, but it feels like the pollen is still getting into my throat. It feels as though the pollen-filled air is entering the mask through the exhalation port, which is simply a flap. Is there supposed to be a filter placed into that circular area highlighted in the photo?

The filters are 3M P100 2097 filters.

Exhalation port

Exhalation port front view

3M respirator

  • 3
    Also put the lawn mowing clothes directly into the washing machine when you're done. Commented Jun 6, 2022 at 5:43
  • osha.gov/laws-regs/standardinterpretations/1994-05-25 I have to wonder about those studies. In my case, pollen is definitely entering the mask through the exhalation valve. I cannot measure how much exactly but definitely far more than was coming in via the filters themselves. The pollen is not coming in via an incomplete seal on the face: when I place my thumb over the entire exhalation valve area (the opening near the pink rectangle in photo #2) and breathe in, the mask collapses against my face. (The exhalation valve is not compromised by paint or other foreign substance.)
    – mr blint
    Commented Jun 6, 2022 at 11:10

1 Answer 1


The exhalation port has a valve (which is typically a thin rubber flap)

Given the design of your filters, you probably need to demount the filters to perform a basic fit and function test by sealing the inlet filter holes (with the palms of your hands, we're not trying to kill you) and inhaling.

If the mask pulls in and you can't get air, all is fitting and working as it should. If you can inhale, you either need a new exhaust port valve, or you have a poor fit. Note that the latter condition is common enough that most industrial site requiring the use of respirators actually have someone who does or oversees the fitting - it's hard to "guess the right size" when ordering online.

  • 1
    This is a pretty new respirator. That it should need a new flap valve is an indication that the exhalation valve is an "Achilles heel" in the design.
    – mr blint
    Commented Jun 5, 2022 at 17:27
  • 2
    Depending how new, you might try complaining to the manufacturer.
    – Ecnerwal
    Commented Jun 5, 2022 at 17:30
  • 6
    @mrblint, speaking as someone who wore a gas mask in the military, you shouldn't have to press the mask against your face. In fact, you don't want to test it like that. The test for a good seal is to not have anything pressing the mask against your face, covering the intake holes, and breathing in. Only if your mask still sucks into your face do you have a good seal. The mask should stay on your face without the straps, except in rapid motion. Also, you should be cleaning it with alcohol swabs (the entire inside) in between uses and kept in a sealed bag, too. Commented Jun 6, 2022 at 15:14
  • 2
    @computercarguy Pressing the mask against my face with my hand and blocking the filter ports with my palms was done only in an effort to eliminate an improper face-seal as the cause of air coming in and to show that the exhalation valve was permitting air ingress. Only after I had blocked the exhalation port as well did air stop coming in.
    – mr blint
    Commented Jul 1, 2022 at 14:17
  • 1
    @computercarguy: I am not having to do that at all. It was to ensure that absolutely no air was entering via the face seal during the testing to determine whether air was coming in through the exhalation valve when I inhaled. And now that I've covered the exhalation valve area with fabric cut from an N-95 mask, the problem is gone. The exhalation valve was indeed the Achilles heel in the design that I suspected it was.
    – mr blint
    Commented Jul 1, 2022 at 17:53

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge you have read our privacy policy.

Not the answer you're looking for? Browse other questions tagged or ask your own question.