I quoted this from another thread because it reminded me of something I wanted to bring up last year, but forgot.

We are building a retirement home east of Sierra Vista, AZ at the moment. We are south of Highway 90 and just east of the San Pedro River. The evacuation order the last couple of days included the area west of the river up to the 90 and pre-evacuation on our side. We’re not there yet, so it’s no problem.

The reason for the post is, when we were there last summer, I was checking the tire pressures on the SUV and the top of my foot stared stinging…BAD. I was looking for an ant or scorpion. I didn’t see anything. I bent down to put the cap back on and got stung again. I looked at my foot and there was a bright spot on it. The wheel cover was reflecting a concentrated beam of sunlight on my foot. It’s quite possible that even something as simple as wheel coverings or clear bottles of water could start a fire in that hot, dry, climate.

I don’t think that’s the case in the three large fires in AZ, but it’s something to be aware of. And, no, I have not changed the wheel covers, yet. But I plan to.

"It is said" that broken glass bottle bottoms have started fires in California chaparral by acting as lenses and focusing the sun's rays just right. This may be a rural legend, but it is certainly within the range of possibility. I have also heard that spontaneous combustion has occurred in California chaparral, but that is a little harder to swallow.....

Piezoelectric or static electric discharge combined with exceptionally dry tinder or combustible material especially in very dry air may initiate a fire. Fine airborne dust particles agitating against a structure with some inherent electrical capacitance qualities or even compression of ground minerals in Earthquake zones can cause electrostatic and piezoelectric discharges.

I suspect that even nuclear fallout in a very dry environment with the ability to ionise ground materials could potentially also generate electrical discharges as well.

Can you give references for any verified, real world instances where that occurred, especially in the absence of lightning?

I had a hard time coming up with a title for the thread and probably did a poor job. My point wasn't that fires can be started accidentally, per se, but that objects that we use in the wild every day may be a threat. My SUV sits there day after day and I didn't realize that it may pose a fire threat.

It's just a heads-up to increase situational-awareness.

As some might recall from the movie title "Farenheit 451", that is the ignition point of dry paper (233 °C).
This is a couple of hundred degrees hotter than the 160 °F or so that it takes to feel 'hot'.

My personal opinion is that there is far more igniton danger from your catalytic converter (which can reach 750°F on the outer surface) than there is from your hubcaps.

I have started a fire, under ideal conditions, by concentrating sunlight through the convex bottom of a glass bottle.
It was far from easy, and seems unlikely to occur accidently, but if you wait long long enough, and discard enough broken bottles, then the improbable will eventually occur.

I heard somwhere that most forest or wilderness fires are started by lightning.
The risks of a fire being started immediatly by a lightning strike are of course well known.
Perhaps less well known, is that a large tree struck by lightning may smoulder internaly for MONTHS before conditions become suitable for rapid spread.
Whilst the tree remains standing and the surroundings damp, spread is unlikely, but when the smouldering tree falls onto wind dried leaves etc, then spread is likely.

In areas at especial risk, fire watchers atop towers or in aircraft, search for smoke.
They sometimes find a tree smouldering, weeks or even months after the last thunderstorm.

I have even heard that the occasional forgotten about store of nuts collected by Squirrels can even spontaneously catch fire and even damp bails of hay.

People as well.

NightHiker, I, too, remember reading about that. Just a tad self-centered...

Sue

Compost heaps have been known to heat up to the point of Spontaneous combustion,& Hay when damp,Stacked & then covered also has Spontaneously combusted.I've seen mirrors cook wood planks with tar on them on MythBusters,& I've produced sparks whilst shooting from richocet,I've also ran into 100's of areas in the boonies where, people have set up shooting areas with tons of glass shards blown about,there is always the chance of Magnifacation on clear windless days,of which there are many in the desert!