Are there codes and regulations as far as space/distance when I enclose my furnace in a utility closet?

I'm finishing my basement and want to build a wall around the area where the Oil Furnace, Hot Water heater and chimney are.

I was planning on putting leuver doors at the front of the furnace for access, but I didn't know if there was a specific amount of space that needed to be between the furnace front and the doors?

I live in Massachusetts if that matters at all.

Thanks for your help.

Jeff