An arson expert based in California says firefighter arson is a recognized, ongoing problem, but it's difficult to know exactly how common it is because authorities don't keep records.

Edward Nordskog's comments come in the wake of a 19-year-old volunteer firefighter being charged on Saturday with 18 counts of arson, for a spate of suspicious fires in and around the town of Mayerthorpe, Alta. The fires included a massive blaze that destroyed the CN trestle bridge.

Lawson Schalm, son of a former town mayor, is scheduled to make his first court appearance in Stony Plain provincial court on Wednesday.

Nordskog said he tracks serial arson cases.

Ed Nordskog is an arson expert who has written numerous books on the subject. (Supplied) "There's roughly 100 firefighter arsonists convicted every year in North America and all of them are serial arsonists, which means three or more fires," Nordskog said Monday in a telephone interview.

It's whether the problem is growing or not that Nordskog can't seem to get a handle on. That's because most law enforcement records don't routinely differentiate between arsonists who are firefighters and those who are not.

"Fire agencies historically hid these," Nordskog said.

Research into firefighter arson indicates it's a long-standing problem. Some researchers have recommended national databases or tracking systems be established.

Matthew Hinds-Aldrich, an assistant professor of fire science at Anna Maria College in Paxton, Massachusetts, completed a report in 2011 for the National Volunteer Fire Council (NVFC) that looks into the issue and recommends better tracking as well as prevention practices for fire services.

The NVFC website notes that firefighter arson "is a long-standing problem that impacts fire departments and communities across the nation," suggesting it is "not a new phenomenon."

As part of his work, Nordskog profiles arsonists. He says firefighter arsonists are typically young men who are quite new in the fire service.

'Some are bored, seeking excitement'

The reasons they resort to arson vary, he said.

"There are the heroes, looking for recognition ... some are bored, seeking excitement," Nordskog said. "A lot of arsonists, their motive is sometimes based on a lot of anger and frustration ... or to get rid of stress."

Family history can also play a part because firefighting is a family tradition with a lot of firefighter arsonists, Nordskog explained.

"Some of these guys are trying to live up to the war stories of their parents, or uncles, who may have been in the fire service in the past," he said.

In fact, the advances of fire safety and safer construction materials have greatly reduced the number of fires in North America, Nordskog said.