Watch your upright silos closely the first three to six weeks after putting silage corn, hay-crop silage or any other material into them. But don't neglect them the rest of the year, because silo fires happen "every year and through the year," warns Dave Hill, director of Pennsylvania State University's Managing Agricultural Emergencies program.
Those not noticed soon enough, or not handled correctly, can cause feedstuff losses of $30,000 or more, he adds.
Hill has seen a lot of such fires. He and his team are frequently called out to Pennsylvania farms to help size up just what should be done to contain and put them out. Fires started by spontaneous combustion, usually when the crop is put up too dry and doesn't have enough moisture to dissipate the heat produced through natural fermentation, can be tricky to handle.
"One of the things we try to tell farmers, and especially fire companies, is if you get a silo of fire, there's usually no huge emergency. The product that's in that silo is not a good fuel source. It's not going to go rip-roaring through the silo and burn your entire operation."
Don't, he stresses, let firefighters pump water on your corn silage, because that just helps ruin its feed value and probably won't extinguish the fire.
"If there's a fire inside that silo that's been caused by spontaneous combustion, then it's in a pocket someplace in the middle burning. If you throw a lot of water on top of that silo, in all likelihood, the water is just going to go down the edges of the silo and maybe into the first 6-8" of material. It's more than likely not going to get to the pocket."
Producers have a few hours to get an Extension safety specialist out to help determine the best method of action. He suggests that producers and firefighters download "Silo Fire Decision Tree" charts from the Managing Agricultural Emergencies Web site (under "Quick Links"). The charts, for conventional and oxygen-limiting silos, offer steps to be taken and ask information needed by specialists when they're called.
An essential bit of information needed: whether the burning silo is conventional or oxygen-limiting. Oxygen-limiting silos can be more dangerous and fires in them are treated differently because of the potential for pressure to build and cause explosions.
Fires burning in pockets within a conventional silo can be extinguished using thermal imaging cameras, which can show where the excessive heating is found. A small hole drilled into the silo, and water pumped to that specific pocket, can contain the fire until the producer can safely unload the silage to that spot in the silo.
"It's not real simple, but it's much more effective than flooding the silage. You're trying to find the spot and kind of surgically enter that with your probe.
"All you've created is an inch-and-a-half hole that could easily be plugged up with patching material, and you haven't ruined a whole lot of feed," Hill says.
Fires in oxygen-limiting silos can be treated by closing off all openings to hopefully smother the fire. Or a gas such as carbon dioxide or liquid nitrogen can be pumped into the silo to consume any air that keeps the fire burning. Early detection of fire is critical with these types of silos, he adds.
But don't always assume a fire is created within the silo. Hill says at least a third of those he's handled were started in chutes. Chute fires can be caused by faulty wiring or old crop left within. Because fires can smoke heavily, it's hard to pinpoint when they're in chutes.
It's not fun climbing a chute with an SCBA (self-contained breathing apparatus) on, or washing the chute out, but Hill says those fires are easier to put out than pocket fires within silos.
"If you notice heavy smoke, fire or embers in the chute, that chute will need to be washed out. That will be a terrible mess if you're going to do that from the ground. What we suggest to fire companies is to try to get at the top of the silo and break into the chute, drop some sort of nozzle down from above and wash it out that way.
"When you notice a fire," he concludes, "it's not going to get any worse, for the most part, in a couple of hours. Now, that said, it depends on whether the fire is in an oxygen-limiting silo or a non-oxygen-limiting silo. Oxygen-limiting silos are really a different beast and they're extremely dangerous."
Hill gives farmers further advice in a short paper he wrote called "Silo Fires - Protect Your Investment," which can be found on that same Web site, also under "Quick Links."