Changes recommended after the deaths of two Perth County firefighters in Listowel four years ago are now part of the Ontario Fire Code.

On March 17, 2011, Ken Rea and Ray Walter went inside a burning building to make sure everyone had escaped, but as they searched the roof of the dollar store collapsed on top of them.

Now, changes to Ontario's Fire Code to hopefully prevent a similar outcome have been unveiled.

North Perth Fire Chief Ed Smith says, "It is something good that has come out of the tragedy. The unfortunate part is - it took a tragedy. And we can't bring them back from that."

A investigation by Ontario's Fire Marshal's Office concluded that roofers using a propane torch accidentally started the blaze.

The fire smouldered for over 40 minutes in a tiny space between the roof and ceiling, before ultimately causing the roof to collapse on top of the two firefighters.

Changes to the Fire Code now restrict the use of tar vats or bitumen kettles on roofs. They must keep combustible materials like the propane torch used on the dollar store's roof at least five metres away from the hot tar as well to try and limit the possibility of sparking a fire.

Smith says, "I feel that the code's a very positive change towards providing safety and responsibility to the people that do that type of work."

An hourly fire watch is also required when an open flame or other ignition sources are used during roof tarring.

Bill Hunter, Perth East fire chief, says, "Any type of metal working, welding, cutting, braising, that type of thing - there's usually requirements for fire watch. So basically the concept has just been extended to the roofing industry."

And these may not be the only changes to Ontario's Fire Code as a result of the 2001 Listowel tragedy, with Smith and others fire chiefs pushing for more improvements.

"Placarding on buildings which indicates whether it's of lightweight construction truss-wise, lightweight construction floor-wise, so that when our people pull up on scene they are able to automatically say, 'Here's what we know we're going to be dealing with,'" Smith explains.