PROVISIONS FOR ADEQUATE COMBUSTION & VENTILATION AIR (continued)
The space in the above example is a confined space because the actual BTU/Hr used is more than the maximum BTU/HR the space can support. You must provide additional fresh air. Your options are as follows:
A.Rework worksheet, adding the space of an adjoining room. If the extra space provides an unconfined space, remove door to adjoining room or add ventilation grills between rooms. See
Ventilation Air From Inside Building.
B.Vent room directly to the outdoors. See Ventilation Air From
Outdoors.
C.Install a lower BTU/Hr heater, if lower BTU/Hr size makes room unconfined.
If the actual BTU/Hr used is less than the maximum BTU/Hr the space can support, the space is an unconfined space. You will need no additional fresh air ventilation.
Warning: You must provide additional ventilation air in a confined space.
Ventilation Air
Ventilation Air From Inside Building (Figure 1)
This fresh air would come from an adjoining unconfined space. When ventilating to an adjoining unconfined space, you must provide two permanent openings: one within 12" of the ceiling and one within 12" of the floor on the wall connecting the two spaces (see options 1 and 2, Figure 1). You can also remove door into adjoining room (see option 3, Figure 1). Each ventilation grill or opening shall have a minimum free area of one square inch per 1,000 BTUH of the total input rating of the gas equipment in the confined space.
Ventilation Air From Outdoors (Figure 2)
Provide extra fresh air by using ventilation grills or ducts. You must provide two permanent openings: one within 12" of the ceiling and one with 12" of the floor. Connect these items directly to the outdoors or spaces open to the outdoors. These spaces include attics and crawl spaces. In most cases for direct communication with the outdoors or direct communication through a vertical duct a free area opening of one square inch per 4,000 BTU/Hr of heater input rating for each grill. If a horizontal duct is used, a grill free area or duct opening shall have a free area opening of one square inch per 2,000 BTU/Hr for each grill. Follow the National Fuel Code ANSI Z223.1/NFPA54, Air for Combustion and Ventilation for required size of ventilation grills or ducts.
IMPORTANT: Do not provide openings for inlet or outlet air into attic if attic has a
Figure 2
Figure 1
Warning: Rework worksheet, adding the space of the adjoining unconfined space.The combined spaces must have enough fresh air to supply all appliances in both spaces.
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