Welcome to IAAI’s September 2009 CFITrainer.Net Podcast. This month, two of our stories explore the relationship between climate conditions and fire risk. The third item looks at new research on formulating fireproof walls. Finally, we’ll cover the latest in IAAI news.

A recent article in Farm and Dairy reported that, according to Penn State’s College of Agricultural Sciences, this year’s unusually wet spring and summer weather has caused farmers to store hay that is wetter than normal, increasing the danger of spontaneous combustion. Because the rain has been so frequent, farmers are forced to harvest hay in the brief time it isn’t raining; and therefore, the hay is not able to dry completely in the field before being baled and stored. If the hay was left in the field for a prolonged wet spell, it would deteriorate. Therefore, farmers are forced into the position of having to bale hay whose moisture content is greater than 20%, which is the optimal level for safe and proper curing. At 25% moisture content, stored hay will generate more heat than can be safely dissipated. The University’s Managing Agricultural Emergencies program further reports an increase in barn fires this season, some of which were the result of spontaneous combustion of stored hay.

To learn more about the process of spontaneous combustion of stored hay, we join someone who was with us last month. His name is David Howitt, Professor of Materials Science. David is from UC Davis — College of Engineering.

David thanks for being here with us.

"Oh, you're welcome"

What causes spontaneous combustion of hay?

Well it’s actually a two stage reaction. Hay, if you warm it up to about 120, 130 degrees centigrade will actually start to catch fire. It’s a low ignition material. What has to happen first is there has to be a bacterial reaction, and it’s believed actually to be the same bacteria that were once thought to be associated with the very beginnings life, and turns out they like to eat and feed on hay. The bacteria starts to develop, they continue to grow and funnily enough they actually, they’re like the little lemmings. They eat and digest themselves and they make high temperatures as they do so and finally the temperature actually kills them, and that temperature, coincidentally enough, is within about five or ten degrees of the temperature necessary to start hay burning on its own, and so it’s this two stage reaction – you have the growth of bacteria at the very beginning in the moist hay, hay itself is a very good insulator, it keeps the heat in, bacteria ultimately die, the process continues and then the haystack actually goes up in smoke. The process actually takes about six weeks.

What is the progression of events in spontaneous combustion of hay?

Well at the very beginning if you cut wet hay and bale it what you get is a very nice wet environment which is where the bacteria starts to grow, and then what happens as the time passes and sometimes the temperatures outside will even drop, but the important thing is that inside the haystack, inside the pile of wet hay, it actually gets colder, but it gets more moist and that’s the bacterial environment that’s the best of all – and they love that, and so as long as the haystack is nice and big and keeps the humidity in or keeps the moisture high, even a cold wet, dank haystack will actually be the starting place for these bacteria and that’s when it begins, and the bacteria will probably go on for a couple of weeks before they finally reach that temperature, and as I said, it’s a sort of self-destructive process.

What are some of the indicators that a particular haystack is at risk for spontaneous combustion?

In the very beginning if it got wet. Essentially dry hay, if the moisture level in the hay is less than about 12% or so, then you don’t have a risk of spontaneous combustion because the bacteria can’t survive, and in fact, most hay brokers when they’re selling hay will actually measure the moisture content as well as the protein content so that when they’re selling it to somebody they know what the risk is that perhaps that haystack will go. It typically takes, as I said, it’s about a six week period after the time the hay gets wet to the time that you can have a spontaneous ignition of the hay, and so obviously in the early few weeks of that the only thing you’re going to see is bacterial activity and there will be some warmth in the hay, but it’s only the warmth of, you know, hot water. It’s not the warmth of boiling water, so you would have to stick your hand well into the hay pile, and in fact, people do make thermometers and thermocouple that you can push into a haystack and measure the temperature, and actually after about the third or fourth week the hay will develop a smell of tobacco. It has a sort of molassesy tobacco kind of smell to it that if you, obviously you have to go up to the haystack and poke around a little bit, but you could actually smell that. If you start to see smoke coming from a haystack, you have to be very, very careful because if you start to take the bales out at that point to try and salvage some of them away from the burning areas, that’s when the fires can get really vicious and you can get these little toroids almost they, it’s a toroidal sort of swirling of hot air and gases and that can take a hay barn down very, very quickly.

After the fire, what are the indicators that spontaneous combustion of hay may have been the cause of the fire?

Well there’s the classic indicator, but it’s the hardest to find, and it really is like a needle in a haystack is what will happen at typically close to the source of where the ignition took place, the haystack will get very, very hot indeed and hay does contain quite a large amount of silica, and so what happens is you could actually melt the silica and form what looks like a glass worm and that typically is the classic sign. It’s known as a clinker, and so if you find one of those you can be pretty sure that you actually had a spontaneous ignition. There are other things that you can find as well that are much more common and those look more like a…clinker, and people often call them by the same name, and that’s when you have a honeycomb like structure within the hay because one of the things that is required to keep the spontaneous reaction, combustion reaction going in the hay is the gradual flow of oxygen and if the hay doesn’t allow that to happen, basically the fire will go out and that also is another sign that you’ve had a spontaneous ignition. The little wormy thing is typically no bigger than about an inch long. Sometimes they’re a little bigger, but most of the time they’re about a third of the size of a cigarette, pretty small. The other clinker, the honeycomb structures, they can be as large as, you know, a brick or even bigger. Those can be pretty hefty and you’ll often see those at the base of the haystack.

What questions should a fire investigator ask witnesses to determine if hay spontaneous combustion might have been the cause of the fire?

Right. The big things are, you know, when they got the hay delivered, and of course, you can check back with the weather reports. If you know where the hay came from, you can figure out what its root was, you know, whether or not it came over any high ground, whether it came through areas that had reported rain, whether the hay was covered when it was transported. These sorts of things are helpful. Also, of course, if the hay was uncovered, if it wasn’t kept in a barn and there was a rainstorm some six weeks before then that’s a pretty good sign. So you’re looking for what the weather conditions were about six weeks before the fire is reported. Those are helpful for the investigator. The other thing is, obviously, what they observed, whether they observed the smoke coming from the side of the haystack, whether they noticed it from the interior. Oftentimes if you pour enough water on it quickly enough you can actually douse the fire and then, of course, you only lose some of the hay. In situations like that, then what you want to do is you want to try and dismantle or break in to the hay pile and see where the fire came from, whether there’s more of it in the interior than in the outside, as I said, whether or not there are regions with that molasses tobaccoey smell, which is very typical of the early stages of heating, but if you were to set fire to a haystack, for example, with a match you wouldn’t get that smell. So those are the sort of things you could look for if the pile is partially burned, but if it’s completely burned, you really have to go in what they saw and, you know, at what times there might have been moisture that got into contact with the hay. The main thing one can use for exclusion is if there was no moisture around. If there wasn’t any rainfall. If there was nothing occurring, you know, six weeks to two months before the fire started, then there’s a good possibility that something else was the cause.

Thanks, David, for this critical information, and we really appreciate your contribution over the past couple of months.

"Oh, you're welcome."

Now, let’s turn our attention to another aspect of how climate may affect fire risk.

According to The Desert Sun newspaper, research at the University of California, Riverside has found that air pollution from engine exhaust is directly contributing to increased wildfires in the desert. Here’s how the theory works. Air pollution increases the nitrates in the air. Then it rains, the rain delivers those nitrates into the soil, and plants soak up the nitrates through their roots. Weeds soak up this nitrogen in greater quantities than native plants do. Nitrogen promotes plant growth, which is typically a good thing. In a more temperate climate, rain would routinely flush away these higher levels of nitrogen. But, in this situation, because the desert has infrequent rain, nitrogen accumulates in the weeds and invasive grasses, which helps them grow more rapidly than native plants and spread more seed. These weeds and grasses thereby carpet the desert, which would otherwise naturally have sparse vegetation. This widespread growth of invasive vegetation provides increased fuel for wildfires. The researchers believe that this process has contributed to the increasing frequency of fires in the Southern California desert, which began in the mid-1980s, just as air pollution in that area increased. And, as fires burn the desert landscape that would normally burn very infrequently, it is harder for native plants to recover because they have not adapted to post-fire conditions. The weeds recover faster and the cycle begins again.

Our final news item reports an innovation in the formulation of fireproof walls. ScienceAlert.Com.Au, which covers scientific research from Australia and New Zealand, recently reported that Curtin University of Technology in Australia has developed a form of fireproof concrete made from fly ash, a waste by-product of coal-fired power stations.

The scientists from Curtin’s Centre for Materials Research assert that this type of geopolymer cement is a safer building material in fire-prone areas because it maintains its strength and integrity under fire conditions that cause traditional cement to fail. In addition, the fly ash cement reduces carbon emissions because the production process uses up to 80% less carbon dioxide than standard cement production. Fly ash waste dumped into the environment is also reduced because it is being "recycled" into this new concrete formulation. The Centre is targeting a product release within the next few years.

Finally, let’s close with news from IAAI.

The Fire Investigation Technician professional designation program opens this month. Program requirements and applications are available on the IAAI website, firearson.com.

Opportunities for services as Peer Reviewers are available if you are a US member of the IAAI. Look for an email from IAAI or call the office at 1-800-468-IAAI for more information.

IAAI is also establishing a Speakers Bureau. If you’re interested in speaking or are looking for a speaker on subjects related to fire and arson investigation, look for the Speakers Bureau announcement and application on the IAAI website, again at www.firearson.com, or call 1-800-468-IAAI.

That concludes the IAAI CFITrainer.Net podcast. We’ll see you again next month.