HELP: My Lighters Won't Stay Lit

[massphatness]

I don't really need help, but I do want to understand why.

I recently bought a propane-fired space heater for the garage to ward off the chill of New England winters whilst I enjoy an after dinner cigar. I'm a big fan of the word "whilst", but I digress. Because I'm also a big fan of go big or go home, I probably bought a larger heater than I really needed. This thing pumps out A LOT of heat, and our single stall garage is toasty warm in no time; toasty to the point where I'm comfortable in a t-shirt. (Sans heater, I'd need a full winter jacket to keep warm as the garage is not insulated all that well.)

Here's my problem. Once the garage becomes hot, my lighters refuse to work. I only have torch lighters and have experienced the same problem with all of them, so I know it's not an issue with a single lighter. Quite by accident I discovered that upon opening the garage door, they go back to their old torch-like reliable selves.

Obviously, there's something about the heat (or maybe the humidity?) that's causing the lighters to fritz out. My question is: WHY?

BTW, I've come up with a work around by leaving the garage door open just a tiny crack, but I'm interested in understanding the science behind what's happening.

Thanks.