Hi it's my parents house I live with them again n it's a mess but should I put them!? Keep dad warm when fixing the boiler or will it get too hot or dangerous or is pointless!? Opinions!? Ty --
Any boiler or furnace needs a certain amount of make-up air to maintain flue draft. Too tight a seal in that room could create a CO hazard. A damper/draft check at the least would be advisable if you proceed. Could you duct make-up air from outside to the furnace enclosure?
While he is working on it, to stay warm, sure unless there is going to be fumes for whatever reason. While it is running though, it needs fresh air. Depending on how old and such, even leaving one of those windows cracked could be a good idea.
