I recently noticed that, on the level quarantine, a soldier is using a gas mask similar to a GP-5. Could it be the GP-5 really? I know it doesn't have that valve thing on the side, but I really became curious. Also, notice that the guy is using Altin-style helmet.
I don't think they really use many proper gas masks in the games - they all seem to be fictional ones with elements inspired by actual gas masks (e.g. this one appearing similar but different to the GP-5, the ranger helmets resembling the M10 a little bit, etc.). Also, no need to upload a duplicate image, I've made the same screenshot and uploaded it two years ago here for the gas mask article. :) --Karmazynowy Wilk (talk) 13:03, June 21, 2016 (UTC)