Forest fire season is well underway across Ontario's northern regions, and firefighters typically take advantage of the patchwork of lakes and rivers to draw water to battle the blazes.

Sometimes, however, they literally fight fire with fire.

Equipment like pumps, hoses and water bombers are common tools of the trade, but so is aerial ignition, said Garry Harland, the fire management supervisor at the fire management headquarters in Thunder Bay.

"[It's] just another tool in the toolbox," he said.

That tool is used chiefly to deal with large fires that would be too unsafe, or costly to fight another way, Harland said. 

The tactic is to burn off potential fuel between an existing fire and a body of water, making use of lakes and rivers as natural barriers to fire.

"Fire, left on its own, with all that momentum, will jump a lot of those natural barriers," Harland said.

"But if you get up close to that natural barrier and ignite the fire, a lot of times you can take away the fuel and slow the fire down before it gets there."

Aerial attack

The ignition is typically done from a helicopter, Harland said, either by dropping plastic spherical containers filled with chemicals that combust on the ground, or by using a torch that drops gobs of a flaming mixture of gasoline and a gelling agent.

The practice is only done when conditions are ideal, Harland said.

"There's got to be a lot of conditions in place, and the stars have to line up for it to be used, and to be used properly."

How often it's done can be dictated by how busy a given fire season may be. That is something that Deb MacLean, a fire information officer with the Ministry of Natural Resources and Forestry, said changes from year-to-year.

"It's entirely dependent on the weather. Certainly it also has a factor of human behaviour," she said.

As for this year, provincial data shows it's a more active fire season than last year. But there are still fewer fires than the recent 10-year average.