We took out a boiler in this residence that had failed, and replaced it with a Burnham series 5 commercial boiler. The boiler is in a very small room to try and take its combustion air from, so we put a mechanical louvered air intake in the window and had glass block placed around it. There is an interlock so it has to be proven open before the boiler will be allowed to fire. A new 4'' pad was also installed for the boiler to sit on.