Continuity mistake: When the firefighters go to the house of the first backdraft "victim" you see that he has gone through the windshield of his car. But when we saw him opening his front door and getting hurled away from the house he didn't land anyway near the car.
Continuity mistake: When the fire truck swerves out of the way to keep from hitting a car, and tips over onto its side, we see it precariously balanced on two wheels. When they show a shot of the inside of the fire truck, we see that the fire truck is scraping against the ground. The side scraping against the ground is the driver's side, while the truck rolled onto the passenger side. Then in the next shot we see the fire truck still balanced on two wheels and then it tips and falls onto its side.
Continuity mistake: At the chemical plant fire when Brian climbs the ladder to the roof the angle of the ladder changes. When he gets on the ladder and climbs it is very steep. But in the next shot, when he gets to the roof, the ladder angle has changed.
Continuity mistake: When Brian visits Stephen on his boat, he looks through Stephen's music collection. He puts his can down near the radio, but when he turns back to the camera the can is back in his hand.
Continuity mistake: During the ladder truck crash scene the truck tips to one side & then when everyone crawls out the truck is on the other side.
Continuity mistake: During Brian's graduation drink the bartender hands him a beer whilst ridiculing him about his numerous failed career moves. When the beer is poured it is about two thirds froth but as it cuts to another scene there is only an inch or so. Sufficient time has not elapsed for the froth to die down as it only spans one sentence of the bartender's dialogue.