Installing Door on Home Furnace Room

Have a friend who lives in Vermont and he bought a house that had gas/ hot water heating system. The space where the unit is installed does not have a door. A serviceman stated that he needs to have one installed but he did not know specs. Where can we go to get info on air feed systems, type and rating of doors (existing opening requires a double door to have access to furnace and water heater) and wall covering for interior of room? Any info would be helpful. Thanks.
Replies
The instructions for the heating unit will tell you how much free area of ventilation is needed for the appliance. Then you'll need louvers with at least that much free area. Free area is usually stamped somewhere on the louver. You'll need one louver low on the door (or wall) and one up high.
The building inspector could tell you what is required for materials for the walls, floors, ceiling, and doors. He'll probably specify it in terms of time, such as 1 hour fire rating for ceilings, 45 minutes for doors, or whatever the requirement is. He can help you select materials which meet the requirements.
I suspect that there may not be a requirement for the rating on the door. You can't have a fire rated door with louvers, after all. If there is such a requirement the building inspector can explain how to meet it.