MIRA SAFETY M CBRN Full Face Reusable Respirator-Mask Gas Mask (CM-7M Mask WITH Drinking System)

Q: how long will the filters last once activated?

Every filter is different! You happened to buy the 20-year shelf life MIRA filter, and that shelf-life is for SEALED filters. It beats other companies by like 15 years. The moment any filter is unsealed during any C, B, R, or N situation, the clock on breathable air starts ticking down. Each situation is different and depends on how much C, B, R, or N is presently being filtered. You might have 2 hours or you might have 12 hours. You MUST review the mfg specs and memorize them or print them and keep them always, otherwise you may be walking around filtering ionized radiation from the big city nuke 40 miles away, with zero idea when to replace your filter! At least make sure you have a healthy supply of iodide tablets to max out thyroid absorption. Read the specs. Specs specs specs. Nobody here knows how long you can filter out a dirty bomb from who knows what proximity to it for crying out loud.