I have a comfort air natural gas furnace when it call for heat,their is a loud boom noise,could the hot surface ignitor have a crack or needs replacing?
A dirty burner box can cause a loud noise when it starts because the gas is not traveling and mixing properly as it is released through the burner assembly. As part of a service contract we would use a vacuum and a soft brush to vacuum the burner box out.
IF YOUR FURNACE HAS A HOT SURFACE IGNITOR YOU MUST BE VERY CAREFUL AROUND IT WHILE CLEANING THE BURNER BOX.
There was a couple of times that, due to neglect, the burner assembly was so dirty it had to be removed and washed.