Firefighter here. I will walk into a burning building if I'm wearing bunker gear, breathing from a working SCBA, carrying a Halligan or axe so I can chop my way back out if I have to, and my buddy is with me carrying a hose squirting water. Lots of water. Said hose must be attached to a BRT (big red truck) on the other end so that when I can't see shit and my air alarm starts beeping we can crawl along by feeling said hose and follow it back out to safety.

Most important, I must have a reasonable suspicion that there are lives inside that might be savable.

Without all that, screw it. That building gets to burn.