3M recommends replacing both pancake and cartridge filters within six months of opening their packages (PDF), or, in environments where oil aerosols are present, after only 40 hours of total use or 30 days after the first use, whichever comes first. The cartridges are more expensive and weigh far more-8.6 ounces per pair on our scale-but they’re also sturdier, and they might be the better choice if you’ll be doing strenuous physical work, such as a kitchen demolition, while wearing your respirator. The pancake filters weigh just half an ounce per pair, and they’re our first recommendation for typical use outdoors and around the home. NIOSH approval means that, at the equivalent rating (P100 in this case), pancake-style filters, such as the 3M 2097 filter we recommend, protect you just as effectively as hard-plastic cartridge filters like the 3M 60926. Dip in clean water to activate for a fast and economical mother mold material. Ideal as a general use sculpting medium for art and craft projects. High quality, medical plaster bandages/cloth for lifecasting and moldmaking. And as P-designated filters, they also protect against oil-based substances in the air, such as paint fumes, as well as some caustic vapors. Plaster cloth (plaster of paris tape, gauze, plaster bandage) popularly used in strips to design and strengthen creations. The “100” designation indicates that they capture 99.97% of fine particulates, such as wildfire smoke.

P100-rated filters are the most widely available kind that meet that criterion.

Plaster cloth strips