Yuh know, I have the same problem, I think I am taking a liking to these gasmasks! I've seen a couple really cool looking ones around.
Also, I was playing MGS4 and they had psycho mantis wearin his gas mask in one of the scenes, I was like thats nfpgasmask!!! eerrr
Back on topic. I found that mine was hanging by one bolt one morning. The bolt holes have dry rotted a quick fix was to shove a washer into the hole which is actaully tapered so it worked out just fine...