I have asphyxiphobia. There, I said it, and for some reason it's been very bad the past couple of months. I think I nearly had a panic attack a while back. I never had one before. If I owned a gun I might have shot myself. So there you have it. It comes and goes. It's been much better lately though.
I had a couple of bad experiences when I was a kid that left me without air until I nearly passed out. Those were probably the source of the phobia even though it only started hitting me a few years ago. When you're young you don't think about dying, but now that I'm in those prime heart attack years, I suddenly have this phobia that's hit me. I wrote a very short tidbit about it a couple of years ago (though in a veiled context) within a novelette where one of the characters was afraid that death might be a life after death state of never being able to breathe forever. Could the fires of a real Hell be any worse? I don't believe any of that though. Not really. It's mostly just dying from not being able to breathe that I worry about. Once I'm dead I honestly don't think it will be a problem.
Strange the fears we pick up later in life. A lot of people seem to do it. When we're young we're so fearless.