Classic BULLETIN Article
Air for Combustion and Ventilation
This article by former staff member Lee Doran was originally published in the spring 1994 National Board BULLETIN. Some code requirements may have changed because of advances in material technology and/or actual experience. The reader is cautioned to refer to the latest edition and addenda of the National Board Inspection Code and ASME CSD-1 for current requirements.
One of the many things the boiler inspector observes during an inspection of the boiler is the cleanliness of the boiler room. This is done for several reasons.
Obviously, the state of housekeeping in the boiler room is a clue to the maintenance upkeep and operation. A well-kept boiler room is a good clue that the boiler will also be well maintained and operated, and vice-versa.
A cluttered boiler room or a boiler room used for storage obstructs the free circulation of air and has a detrimental effect on both proper burner combustion and the ventilation for cooling of equipment, in addition to posing a fire hazard.
Obstructions placed in front of the combustion air openings restrict the free flow of air into the boiler room and may cause the burner to not get enough air for proper combustion. When this happens, it will begin to produce soot and carbon monoxide (CO). Both of these products are unburned fuel.
Soot directly affects the efficiency of the boiler. Just a 1/16-inch of soot coating on the heat transfer surfaces can cause an 18 to 20 percent loss in efficiency. Carbon monoxide is a poisonous, odorless gas, and is extremely dangerous and deadly. Carbon monoxide has caused serious injuries and death.
If the inspector finds obstructions in the combustion air openings, clutter in the boiler room, or finds that the boiler room is being used for storage or is in an otherwise poor state of housekeeping, the inspector should explain the hazards and potential consequences to the owner/user.
Remember, the boiler room is for the boiler and should never be used for storage. This is a serious problem, particularly in public schools where principals, teachers, and coaches find the boiler room a convenient place to store miscellaneous materials.
ASME CSD-1a-1993, Controls and Safety Devices for Automatically Fired Boilers, paragraph CG-260 addresses the requirements for combustion air. It states that combustion air requirements must be in accordance with ANSI/NFPA-54, National Fuel Gas Code for Gas Fired Boilers, and ANSI/NFPA-31, Installation of Oil Burning Equipment for Oil-Fired Boilers.
In addition, CG-260 requires that: “Louvers and grills shall be fixed in the opened position or interlocked so that they are opened automatically during equipment operation. The interlock shall be placed on the driven member and fans supplying air to the boiler room for combustion shall be interlocked with the burner, so that air flow is proven during equipment operation.”