The sun is actually not much of a factor in there. What makes this happen is that the mulch rots which is an exothermic process and it insulates very good as well. So the core temperature of pile will slowly creep up until you reach the ignition point. The same will happen to bales of hay that are taken from the field too wet.
What makes this happen is that the mulch rots which is an exothermic process and it insulates very good as well. So the core temperature of pile will slowly creep up until you reach the ignition point.
Absolutely true. But while I wouldn't even be able to begin quantifying the degree to which the radiant heat from the sun is a factor, I strongly suspect that it is a factor, if for no other reason that the observation that we only went to those fires in summer months. But, to be fair, there could be a million other confounding factors.
Whether or not a given system ignites on a given day depends on many things: ambient temperature, wind, humidity, presence of accelerants, yadda, yadda, yadda.
I suspect this is one reason why it's so hard to get people to take fire safety seriously: that pile of oily rags in the corner? It's not going to catch fire. This time. Or next time. Or next time. And so on... until it does. So people get complacent because "hey, the oily rags never caught fire before, why would I expect them to today?" Disconnect the sprinkler system? Sure, why not - the building isn't going to catch fire. This time...
I know the former head fire marshall of a major European city (2M inhabitants). The stories about root causes have made me extra fire safety sensitive and it is a continuous source of frustration to me that others don't take this stuff as serious. Cheap power adapters are somewhere near the top of my paranoia list, anything rechargeable battery operated a close second.
So what's the procedure like? Pull them apart and then put it out? I'd assume that if you just wet them from the outside you are just setting yourself up for a speedy return to the same location.
So what's the procedure like? Pull them apart and then put it out?
Exactly. Besides trapping heat in, the hay also forms a fairly effective barrier against water getting inside. If you don't rip the bale apart to fully extinguish the seat of the fire, you just wind up right back out there.
You can see the process underway in this video, where a bunch of hay bales caught file while on the back of a truck being transported. Scroll a few minutes into the video and you can see where they brought a front-end loader out there to start ripping the bales apart.
Using a "wetting agent"[1] also helps, and some departments will use store bought dish soap, like Dawn, for that purpose (purpose made firefighting foam is kinda expensive).
Interesting video, especially with a drone over so much hot air. Amazing how much land is already gone. And the truck itself is just a memory while plenty of the bales of hay are still sitting around unharmed, you can really see the 'R' value at work there.
It almost looks as though the fire started in the truck itself or on one of the rear brakes, was there a report on the cause of the fire in this particular case?
edit: amazing coordination as well, at one point working on the fire in four different places.
It almost looks as though the fire started in the truck itself or on one of the rear brakes, was there a report on the cause of the fire in this particular case?
