A firefighter going back into the fire in the opening scene does not reconnect his SCBA regulator or reattach his mask when reentering the fire, but comes back out with both attached.
Chief Flynn is wearing a lieutenant's bugles (a single bugle) on his lapel pins. As a Chief, he should have a minimum of two crossed bugles (signifying a Battalion Chief).
Firefighters coming out of the fire in the first scene have their SCBA masks disconnected from the strap mounts on the side of the mask. The Scott AV2000 masks that they are using do not disconnect that way during normal use, and instead are loosened and taken off the top of the head.