UNVENTED (VENT-FREE) FIREBOX
AIR FOR COMBUSTION AND VENTILATION
Continued
VENTILATION AIR
Ventilation
Grills
Into Adjoining
12"
Ventilation Grills
Into Adjoining Room,
Room,
Or
Option 2
Ventilation Air From Inside
Option 1
Remove
Building
This fresh air would come from an adjoining unconfined space. When ventilating to an adjoining unconfined space, you must pro- vide 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 4). You can also remove door into adjoining room (see op- tion 3, Figure 4). Follow the National Fuel Gas Code NFPA 54/ANS Z223.1, Section 5.3, Air for Combustion and Ventilation for required size of ventilation grills or ducts.
WARNING: Rework work- sheet, adding the space of the adjoining unconfined space. The combined spaces must have enough fresh air to supply all appliances in both spaces.
Ventilation Air From Outdoors
Provide extra fresh air by using ventilation grills or ducts. You must provide two per- manent openings: one within 12" of the ceiling and one within 12" of the floor. Connect these items directly to the outdoors or spaces open to the outdoors. These spaces include attics and crawl spaces.
IMPORTANT: Do not provide openings for inlet or outlet air into attic if attic has a
Door into Adjoining Room, Option 
3
12"
Figure 4 - Ventilation Air from Inside Building
Ventilated
Outlet Attic
Air
Outlet |
|
Air | To Attic |
|
To
Crawl
Space
Inlet
Air
Inlet Air |
| Ventilated |
|
| Crawl Space |
|
|
Figure 5 - Ventilation Air from Outdoors
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