Continuity mistake: Casey and Seagar run down the stairs leading to the parking garage. Seagar passes the 15th floor twice (large sign on the wall).
Continuity mistake: One of the protesters approaches Chief Boden twice.
A Real Shot in the Arm - S8-E2
Continuity mistake: When Sylvie and her ex hometown friend are having milkshakes, both milkshakes keeps switching back and forth between full with whipped cream and a cherry (when Sylvie is in view) and partially full with melted whipped cream and no cherry visible (when her friend is in view). (00:20:00)
Continuity mistake: The entire fire house is in the hospital waiting room for word on Otis. Chief Boden sits down twice next to Casey.
Answer: Internet sources give many reasons why firefighters do this, but in regards to your question, it's probably because opening walls and ceilings creates better ventilation which allows heat and smoke to escape, giving firefighters better visibility and lowering the temperature.
raywest ★