Painting Protection - how long will Respirator Filters last?

Hi Guys,

I've been priming the Dart, and then it dawned on me that I really didn't know how viable my filters were in the respirator :(. I have a MSA Comfo Classic, with P100 Filters. The respirator is about 5 Years old, but only used for 15 mintues. When I was finished I sealed in a ziplock bag. I was spraying epoxy primer last night, and never detected any fumes penetrating the cartridges.

In the Military, our Nuclear, Biological, Chemical protective masks filters are normally rated for 6 hours (continuous use in a contaminated area). Tried to research it on the Internet, but couldn't find any good info.

Thanks