Is it okay to use a gas mask filter for a costume, or even an expired one? - Quora
Russian Gas Mask Canister Filter GP-7k 40mm with box for gp-5/gp-7/gp-9/ppm-88 – Seller-bay.com
Mask of Horror: The Soviet GP-5 | Guide Outdoors
User blog:MystedCynic/How to SAFELY disassemble GP-5 filter | Gas Mask and Respirator Wiki | Fandom
Igor Pogrebelnyi - "Filter GP-5" [gasmask filter]
What's inside a GP-5 filter? - YouTube
Paul Graham on Twitter: "Many thanks to the people who've warned me that old gas mask filters can contain asbestos and other nasty things. This one is a GP5, whose filters do,