Looking for advice on respirator types for using a Dremel on fiberglass.

I was reforming the fiberglass seat in my all-fiberglass kayak, using a small Dremel cutting wheel and sanding drum attachment. Created a great deal of dust, so I wore my 1/2 face North Respirator with particulate (P100)cartridges. (It's an old one, perhaps not made for sanding but I check the seal whenever I use it - cover the intake cartridges and make sure the exhale opening isn't leaking). In doing this Dremel work the cutting action created a strong smell - a bit like a chemical/resin smell but also perhaps like burning. But the kayak is 13 years old - so there shouldn't be any uncured resin that would generate a smell when sanded/cut(?). (I assume it's polyester resin, it's an old VCP kayak). I am wondering if my respirator was actually leaking allowing the dust to get it, hence the smell? Or if the action of the Dremel tool could have generated a vapor that wasn't blocked by my particulate filter? Isn't smoke a particle - and therefore the smell may indeed have indicated a leak? Can a Dremel tool release resin vapors despite the fiberglass being many years old?

When I do new (wet) fiberglass/gelcoat work I use OV cartridges on my respirator, and no smell gets through.

I was covered in dust after cutting/sanding away at this thing for over an hour - tossed the clothes in the wash. Just wondering why there was a smell and if I should throw out my 6+ year old respirator (that seems to be fine on visual inspection.)

Any thoughts would be appreciated. Thanks. JIM