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5
WARNING: Rework worksheet, add-
ing the space of the adjoining
unconfined space. The combined spaces
must have enough fresh air to supply all
appliances in both spaces.
VENTILATION AIR
Ventilation Air From Inside Building
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 2). You can also
remove door into adjoining room (see
option 3, Figure 2). 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
Example:
Gas water heater 40,000 Btu/Hr
Vent free heater + 20,000 Btu/Hr
Total = 60,000 Btu/Hr
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.
3. Add the Btu/Hr of all fuel burning appliances in the space.
Vent-free heater Btu/Hr
Gas water heater* Btu/Hr
Gas furnace Btu/Hr
Vented gas heater Btu/Hr
Gas Fireplace logs Btu/Hr
Other gas appliances* + Btu/Hr
Total = Btu/Hr
*Do not include direct-vent gas appliances. Direct-vent draws combustion air from the outdoors and
vents to the outdoors.
4. Compare the maximum Btu/Hr the space can support with the actual amount of Btu/Hr used.
Btu/Hr (maximum the space can support)
Btu/Hr (actual amount of Btu/Hr used)
Example : 51,200 Btu/Hr(maximum the space can support)
60,000 Btu/Hr(actual amount of Btu/Hr used)
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, page 5.
B. Vent room directly to the outdoors. See Ventilation Air From Outdoors, page 6 .
C. Install a lower Btu/Hr heater, if lower Btu/Hr size makes room unconfined.
Figure 2 -Ventilation Air from Inside Building