I know this isn't strictly speaking a plumbing question, but thought you might be able to help anyway... My friends just bought a new loft style apartment in NYC where each apartment has its own gas fired boiler to supply hot water for the radiators. Unfortunately, their boiler (furnace?) is in a closet off of their bedroom, approximately 3 feet from their bed. It seems to be one of the newer kind with horizontal flue venting out a side wall. It also has a 4" fresh air supply duct that draws air from outside for combustion. This furnace, the hot water tank and an expansion tank are all housed in a 4' by 3' closet.

Ok, so here's the question: currently the door to this closet has a louvered grate on it. They would like to replace with a solid door to help reduce the noise (since its so close to their bed). Is this a problem? Since there is a fresh air supply coming from outside, seems like the louver in the door might not be necessary? Who could they ask for info? Manufacturer of heater? Or is this generally just a bad idea?