If you cough or blow your nose & see brown dust in your hanky afterwards, it means you should have worn a mask. I have seasonal allergies & asthma so I do wear N95 masks whenever I am running sanders, spray painting, or when shoveling/cleaning in coop or pigeon loft. A few times I had only planned on briefly scooping under poop perches, but then decided to do more...well you know if you kick up dust, the PDZ stuff, & see it in the air, or wheeze & find you need to get some fresh air outside, you might as well get a mask. It is worth it, give your lungs a break.