I've always found gas masks a bit scary. They look like they were designed to look as menacing as possible. Like a terminator pig from Hell or something. I also remember the horror stories from the army when the officers told us that we had to eat our own vomit if we puked in the gas masks during the tear gas tests.
Check this out:
http://www.gasmasklexikon.com/
Take a look at the 'USA MIL': M2-10A1-6. It would be enough to scare off all post-PO zombies without firing a single shot. If you want to visit the Blue Oyster Bar (known from Police Academy) I'd recommend the Dutch (Netherland) "Volksgasmasker". Look how nicely the mask matches the suit...





