2.2 dETErmINING CONFINEd Or uNCONFINEd SpACE
To determine the volume of the room where the heater is to be installed, multiply the width x the length x the ceiling height
of that room measured in feet. If any adjoining rooms are connected by grilles or openings such as kitchen pass-throughs,
etc., the volume of those rooms may be added to the total.
Multiply the room volume by 1000 and divide this amount by 50 to determine the maximum BTU/hr that the space can
support with adequate combustion and ventilation air.
Add the Btu/hr of all fuel burning appliances located within the space such as gas furnace, gas water heater, etc. Do not
include direct vent gas appliances which draw their input and output air from and to the outdoors.
!
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 construction, provide adequate combustion and ventilation air by one of the
methods described in the National Fuel Gas Code ANSI Z223.1, Section 5.3 or the applicable local code.
Unusually tight construction is defined as construction where:
A)
Walls and ceilings exposed to the outside atmosphere have a continuous water vapour retarder with a rating of 1 perm
(6 x 10-11 kg per pa-sec-m2) or less with openings gasketed or sealed, and
B)
Weather stripping has been added on openable 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.
An unvented room heater is recommended for use as a secondary heat source rather than as a primary source. Gas
combustion produces water vapour which could occur at the rate of approximately one ounce of water for every 1,000
BTU/hr of gas input. During the cold weather season, indoor humidity levels tend to be low. Consequently, this water
vapour can enhance the living space. However if a problem should occur:
A)
Ensure sufficient combustion and circulation air
B)
Use a dehumidifier
C)
Do not use the unvented room heater as a primary heat source
Without sufficient fresh air for proper operation, poor fuel combustion can result. Carbon Monoxide is a result of poor
combustion.
If additional fresh air is required, use one of the methods described in the National Fuel Gas Code, ANSI Z223.1, Section
5.3 or the applicable local code.
L E N G T H
H E I G H T
ROOM 2
ROOM 1
W I
D T
H
Room Volume = Length x Width x Height
Max BTU/hr = Room Volume x 1000 / 50
If for example:
The length of the rooms is 10 feet,
The width of Room 1 is 10 feet,
The width of Room 2 is 15 feet,
The height of the rooms is 8 feet.
The volume of Room 1: 10x10x8 = 800 cubic feet
The volume of Room 2: 10x15x8 = 1200 cubic feet
TP - DETERMINING CONFINED OR UNCONFINED SPACE
fIgurE2.2
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W415-0204 / F / 10.23.08