Continued, Conﬁned and Unconﬁned Space

AIR FOR COMBUSTION

AND VENTILATION

Continued

Conﬁned and Unconﬁned Space

The National Fuel Gas Code, ANSI Z223.1/NFPA 54 deﬁnes a conﬁned space as a space whose volume is less than 50 cubic feet per 1,000 Btu per hour (4.8 m3 per kw) of the aggregate input rating of all appliances installed in that space and an unconﬁned space as a space whose volume is not less than 50 cubic feet per 1,000 Btu per hour (4.8 m3 per kw) of the aggregate input rating of all appliances installed in that space. Rooms com- municating directly with the space in which the appliances are installed*, through openings not furnished with doors, are considered a part of the unconﬁned space.

*Adjoining rooms are communicating only if there are doorless passageways or ventilation grills between them.

DETERMINING FRESH-AIR FLOW FOR FIREPLACE LOCATION

Determining if You Have a Conﬁned or Unconﬁned Space

Use this work sheet to determine if you have a conﬁned or unconﬁned space.

Space: Includes the room in which you will install ﬁreplace plus any adjoining rooms with doorless pas- sageways or ventilation grills between the rooms.

1.Determine the volume of the space (length x width x height).

Length x Width x Height =__________cu. ft. (volume of space)

Example: Space size 16 ft. (length) x 14 ft. (width) x 8 ft. (ceiling height) = 1792 cu. ft. (volume of space)

If additional ventilation to adjoining room is supplied with grills or openings, add the volume of these rooms to the total volume of the space.

2.Multiply the space volume by 20 to determine the maximum Btu/Hr the space can support.

__________ (volume of space) x 20 = (Maximum Btu/Hr the space can support)

Example: 1792 cu. ft. (volume of space) x 20 = 35,840 (maximum Btu/Hr the space can support)

3.Add the Btu/Hr of all fuel burning appliances in the space.

Vent-free ﬁreplace	___________ 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. Di- rect-vent draws combustion air from the outdoors and vents to the outdoors.

Example:
Gas water heater		30,000	Btu/Hr
Vent-free ﬁreplace	+	10,000	Btu/Hr
Total	=	40,000	Btu/Hr

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: 35,840 Btu/Hr (maximum the space can support)

40,000 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 maxi- mum 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 adjoin- ing 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 8.

B.Vent room directly to the outdoors. See Ventila- tion Air From Outdoors, page 8.

C.Install a lower Btu/Hr ﬁreplace, 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: If the area in which the ﬁreplace may be oper- ated is smaller than that deﬁned as an unconﬁned space or if the building is of unusually tight construction, provide adequate combustion and ventilation air by one of the methods described in the National Fuel Gas Code, ANSI Z223.1/NFPA54 Section 5.3 or applicable local codes.

116658-01A