Ontario's fire marshal has launched an investigation into whether public safety is at risk as a result of the resignations of "double-hatters" -- just as four Ottawa firefighters have agreed to union demands that they quit volunteering at rural volunteer fire departments.

Fire marshal Bernard Moyle has sent inspectors to the Ottawa Valley to look at whether rural forces are being compromised by the union's bid to stop professional firefighters from volunteering outside the city on their own time, a practice known as "double-hatting."

"If they are jeopardizing these people in small communities, then I have a responsibility to tell the government," Mr. Moyle said. "It's up to the government to decide if they are going to deal with this situation."

For two years, Mr. Moyle has been calling for legislation in Ontario to protect double-hatters from dismissal; every other province and territory, except Newfoundland, has such a law.

Mr. Moyle called his investigation in the wake of news that the Ottawa Professional Fire Fighters Association in September threatened five of its members with loss of their jobs if they didn't stop moonlighting.

Yesterday, Fred LeBlanc, president of the Ontario Professional Fire Fighters Association, said four of the five have agreed to comply by the end of the year. They have agreed to gradually "phase out" their volunteer work, he said. The fifth did not respond to the letter; if the union is told he won't quit the volunteer job, it might take action, Mr. LeBlanc said.

"We encourage the locals to lay the charges in those situations," Mr. LeBlanc said. "If the local is frustrated enough, they can lay the charges."

Firefighters can be charged with violating an article in the union's constitution that bans volunteer or part-time work in firefighting, emergency services and policing.

The constitution doesn't outlaw other types of work done outside of firefighters' full-time jobs. Two firefighters with the Stratford fire department were charged by the union with double-hatting in September and there have been more than two dozen charges laid since double-hatting was outlawed by the union's constitution in 1992, Mr. LeBlanc said.

He would not say which rural departments the Ottawa firefighters were volunteering with.

Rural fire chiefs in the Valley are saying that they estimate between 10 and 25 per cent of their volunteers might resign because of the union effort.

Mississippi Mills fire Chief Art Brown said he is worried that 14 out of his 53 firefighters could be forced to resign.

The chief administrative officer in Clarence-Rockland said the municipality is worried that six of its fire department's 60 volunteers could resign; some already have, he added.

"We're losing key people in key positions," said Dan Gatien. "People who provide training and leadership."

The Russell fire department says it has lost two senior firefighters in 18 months. Chief Bruce Armstrong said that until this week, only four firefighters from his department could be expected to respond to weekday fires.

"We don't want to interfere with the collective bargaining process, and we are fairly confident that (municipal and fire officials) can resolve the matter by talking about it," Andrew Hilton said.