Smoke fills a room, leaving firefighters to blindly search for two unconscious people.

It’s a very real situation that could happen at a moment’s notice, which is why for the next eight weeks, Barrie firefighters are practicing at the downtown bus terminal.

"We kind of have a saying, ‘train like your life depends on it because it does.’ So we try to make it seem as realistic as possible," says firefighter Mark St. Germain.

To do that, firefighters are wearing balaclavas to mimic smoke.

"When we're blacked out like this it's actually harder. Sometimes you are in a situation when there is little to no visibility," says firefighter Luke Saunder.

Over the span of a week, about 130 firefighters will participate in this training.

"We are doing an advancing of a charged line, trying to get into an interior attack under basically three minutes from the time they arrive on scene,” says Capt. Domenic Filippelli.

"Practice makes perfect. So you know finding your mistakes here and correcting them before the real thing happens, and getting to know your crew," says firefighter Matt Blank.

These aren't routine exercises. Each scenario is carefully thought out to help prepare crews for real calls.

"It’s very intense.  A healthy bit of fear, but fear in such a way that we're trained for it."