I checked out the compost thing a couple of years ago when I was planning to put a compost pile near a building. All the studies indicated that any pile less than 7'x'7'x7' would not ignite.

Apparently, the biggest offender was green hay stored in a barn. When too green, it starts to compost and the internal temperature rises high enough to spontaneously combust, and there goes another barn. Not to mention the hay.

Sue

Mythbusters showed soda cans, polished with chocolate, being used as a firestarter. Also, an ice lens used like a magnifying glass. However, while I am not going to start littering, I am not going to much worry about pop cans and ice starting major forest fires.

I am more worried about off road vehicles in dry brush, irresponsible campers with fires, people burning garbage in 55 gallon drums in the summer during a drought, careless smokers tossing butts out windows, and kids playing with matches.

The ignition of a wildfire around here that eventually burned 21,000 acres (the Wolf fire) was attributed to sparks generated by target shooting at metallic objects.

I worked on a project a few years ago where we were using hand tools in rocky grassland. We definitely were throwing off sparks fairly regularly. Fortunately no fire resulted, but we were watching.

I wonder what the ignition temp is of dried grass. I held some paper at the focus of the reflection and, after several minutes, got a bit of scorching. I should have tried the dried grass. A saving point is that the apparent motion of the sun would not keep the focus in one spot for very long.

I agree with your point about the CC, but it is not sitting there, hot, for 6 to 8 hours a day.