The Truth about Charcoal and Spontaneous Combustion

Seaworthy, the damage avoidance magazine published by BoatU.S. Marine Insurance, recently reported the findings of a study that looked at the causes of boat fires. Some BoatU.S. members took the report to task for what they thought was conspicuously absent - there were no vessel fires reported as a result of improperly stored charcoal spontaneously combusting. As a follow-up, the current issue further investigates the spontaneous combustion question, and sets the record straight.
"In doing our boat fire study, we couldn't find any claims for fires that were caused by charcoal self igniting," said Marine Insurance Technical Director Bob Adriance. "But some of our 550,000 members believed that it was a concern, so we had the responsibility to investigate the issue further."
Since the BoatU.S. fire study had already viewed thousands of BoatU.S. claim files over 10 years, Adriance and his team next went online in search of definitive leads on the subject. What they found was striking: "Hundreds, perhaps thousands of hits for charcoal/spontaneous combustion," says Adriance.
A warning from a local New York fire department was typical: "Keep damp or wet coals in a well-ventilated area. During the drying process, spontaneous combustion can occur in confined areas." A barbecuing safety page further recommended, "Store charcoal in a metal container with a tight-fitting lid." The team learned there were over 500 charcoal/spontaneous combustion warnings at various web sites. Even with the understanding that online information is often unverifiable, these were warnings from reputable organizations, including many local fire departments. But while the origins of most boat fires could easily be found, what was lacking was any hard data on the charcoal subject.
It wasn't until Adriance found research presented by P.J. Pagni, a professor at the University of California, Berkeley, did the definitive answer come forth.
At a National Fire Protection Association (NFPA) sponsored symposium held at Worcester Polytechnic Institute in Worcester, Massachusetts in 2002, Pagni's research found that the largest commercially available bag of charcoal briquettes (20 lbs.) cannot self-ignite at a temperature below 250. All tested variations: Size, different formulations, addition of water or dry wood, aging, and different bag configurations, raised the already high temperature bar for spontaneous combustion above 250. At normal temperatures (approximately 77F), Pagni's data showed that a bag of charcoal briquettes would have to exceed the volume of a typical house to self-ignite.
Pagni's conclusion is reflected in the 19th edition of the NFPA Fire Protection Handbook which states that, "spontaneous combustion of charcoal sold to consumers is not a possibility because of its processing, small quantity and container."
So why do so many boaters -- and firefighters -- believe that charcoal can spontaneously combust?
"Charcoal's first cousin -- coal -- has a well documented history of self-combustion when damp or stored in large quantities," says Adriance. "It's likely that since the two are similar looking, have similar burning characteristics and even same sounding names, the combustion properties can easily be confused."

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