Discussion
Random question for the more knowledgeable: how often/when do you replace carbon cartridge air filters on P100/carbon respirators? (used occasionally for painting, hazardous vapors, etc.). Is this basically a "replace once you've used them"?
(I assume of course any "real" hazardous conditions you replace before using them, but I'm more... hot peppers and occasionally painting outdoors)
Dunno, but when we were doing those California wildfire days of orange skies and purple noontime sun, my cartridges would rapidly flow less and less air as they loaded up with particles.
Definitely before that point.
@ai6yr
You can take a look at the 3M sheet for official guidelines: https://multimedia.3m.com/mws/media/150751O/reuse-of-organic-vapor-chemical-cartridges-technical-data.pdf?fn=TDB142.pdf
My personal take: it depends on what you are protecting against. For hot peppers, you'll get a heads up that it's time to change, ditto for many solvents. You'll know when it's starting to break through.
That's not a good strategy for serious nasty stuff, however.
@PaulWermer Aha! Answer is probably "throw these out, get new ones for the hot peppers"
@ai6yr in emergency services at my place we use filters only for known hazards that can be felt, smelled or tasted when the filter has been breached/saturated, so then that's what tells you to swap them.
for P3 (european standard, should be like P100?) I remember it being a thing that they just clogg up over time, so if they get hard to breath through, that's another indicator, too.
Now something I'm not accustomed to is occasional use of carbon filters - for those I'd suggest looking up if there's something in manufacturer's manuals? They might only indicate a period that the filters should be good for, though that may assume continued use, making it plausible to neglect moisture drawn during storage, which idk how much impact that has.
Also if there's any other responses I'm curious 
@ai6yr either as soon as you start to smell VOCs through the mask, or after about 40 hours of use. Also, they go bad in open air, so store them in an airtight container when not in use.
@mfitts @ai6yr Advantage to hot peppers is nonlethal and you will know soon enough if the seal is bad or the filter is not working.
I thought that barring damage (cracks, mould, whatever) the filtration is supposed to keep working even after the 40h line (which is the value you'll find on the papers in the cartridge package, somewhere in the fine print) but it starts taking more pressure to inhale through. That was based on N95 studies (manufacturer recommended "max 8h of wear" retained filtration nearly indefinitely, it was fit/seal that failed first) and extrapolating to P100s. I haven't actually looked at studies though and @mfitts if I've been mistaken about this I would love to be corrected!
@ai6yr I think the chemical cartridge filters for my respirator were supposed to be good against EGDN fumes and some other stuff for about 16 hours of use, according to their original package. I'm retired now, so I figure my old respirator can do anti-virus filtering with old P100 filters even if I ought not to wear it around blasting agents.