8.0 COMBUSTION AND VENTILATION AIR

This heater shall not be installed in a confined space or unusually tight construction unless provisions are provided for adequate combustion and

ventilation air. The heater may be located in unusually tight construction provided the space is unconfined, or if confined, is provided with two permanent openings communicating directly with an additional room(s) of sufficient volume so that the combined volume of all connected spaces meets the criteria for an unconfined space, (National Fuel Gas Code NFPA 54 / ANSI Z223.1 - latest edition, Section on Air for Combustion and Ventilation. Generally 50 ft3 per 1,000 BTU input of all operating appliances in the space.

The National Fuel Gas Code, ANSI Z223.1/NFPA 54, defines a confined space as a space whose volume is less than 50 ft3 per 1,000 BTU/Hr (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 ft3 per 1,000 BTU/Hr (4.8 m3 per kW) of the aggregate input rating of all appliances installed in that space.

Rooms communicating directly with the space in which the appliances are installed, through openings not furnished with doors, are considered a part of the unconfined space.

Unusually tight construction is defined as construction where:

a.Wall and ceilings exposed to the outside atmosphere have a continu- ous water vapor retarder with a rating of one perm (6 X 10-11 kg per pa-sec-m2) or less with openings gasketed or sealed;

b.Weather stripping has been added on operable windows and doors; and

c.Caulking or sealants are applied to areas such as joints around window and door frames, between sole plates and floors, between wall ceiling joints, between wall panels, at penetrations for plumbing, electrical, and gas lines, and at other openings.

Use the following equations to determine if you have a confined or unconfined space.

1.Determine the volume of space — ft3.

Length x Width x Height = _____ ft3

(Include adjoining rooms with doorless passageways or ventilation grills between rooms).

Example: 24' (L) x 16' (W) x 8' (H) = 3072 ft3

2.Divide the volume of space by 50 ft3 to determine the maximum BTU/Hr the space can support.

______ (volume of space – ft3)/ 50 ft3 = (Maximum BTU/Hr the space can support)

Example: 3072 ft3 / 50 ft3 = 61.44

or 61,440 BTU/Hr the space can support.

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

Vent-Free heater

_______ BTU/Hr

Gas appliance #1*

_______ BTU/Hr

Gas appliance #2 +

_______ BTU/Hr

Gas appliance #3 +

_______ BTU/Hr

Total =

_______ BTU/Hr

Example:

 

 

Vent-free heater #1

9,000

BTU/Hr

Vent-free heater #2

23,000

BTU/Hr

Gas appliance #1

35,000

BTU/Hr

(water heater)

 

 

Total =

67,000

BTU/Hr

*Do not include direct-vent gas appliances. Direct-vent is sealed com- bustion and draws combustion air from the outdoors.

4.Compare the maximum BTU/Hr the space can support with the actual amount of BTU/Hr used.

_______ BTU/Hr (max. the space can support)

_______ BTU/Hr (actual amount of BTU/Hr used)

Example:

61,440 BTU/Hr (max. the space can support)

67,000 BTU/Hr (actual amount of BTU/Hr used)

The space in the previous 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:

a.Rework equations adding the space of adjoining room(s). If the extra volume provides an unconfined space, then remove door or add ventilation grills between rooms. Refer to National Fuel Gas Code, ANSI Z223.1/NFPA 54-latest edition, Section "Air for Combustion and Ventilation".

b.Vent room directly to the outdoors. Refer to National Fuel Gas Code, ANSI Z223.1/NFPA 54-latest edition, Section "Air for Combustion and Ventilation".

c.Install a lower BTU/Hr heater to make the area an unconfined space.

If the actual BTU/Hr used is less than the maximum BTU/Hr the space can support, then the space is an unconfined space. You will need no additional fresh air ventilation for an unconfined space.

WARNING

If the area in which the heater may be operated is smaller than that defined as an unconfined space or  if  the  building  is of unusually tight construc- tion, provide adequate combustion and ventilation air by one of the methods described in the national fuelgascode,ANSIZ223.1/NFPA54,AirforCombustion and Ventilation Or applicable local codes.