The Chino Valley Unified Fire District certainly has a lot of experience in dealing with spontaneous combustion fires because a very high percentage of fires of this nature are caused in manure piles on dairy ranches
"Basically when you have organic matter, such as manure, hay grass, et cetera, when it gets wet it tends to generate heat," explained Chino Deputy Fire Marshal Kevin Smith. "There's a chemical reaction that will cause the heat to increase, especially if it is all piled up together and that heat will continue to rise. Now as the heat continues to increase, especially if this is in a deep-seeded pile where the manure in the center of the pile doesn't have the ability to cool down by being exposed to cooler air on the surface, it will continue heating up until it hits what's called 'ignition temperature.' At that temperature it catches on fire without being exposed to a spark or a flame."
When the fire starts in large manure or hay piles they are stubborn and it can take a long time and a lot of water to put out.
"Especially when the wind's blowing the way it is, it spreads rapidly," said Capt. Andrew Schuler, Chino Valley Fire. "A lot of times we have to get a tractor out there and it takes a lot of water and we have to use water additives to make the water wetter to get down to the deep-seeded fire."
On dairy farms, manure is put into piles for a long period of time before it can be sold for fertilizer or its methane gas content. And the weather often intervenes.
If it was a mulch fire and not a manure fire, so common in this area, dairy farmers here are breathing a collective sigh of relief.