4
AIR FOR COMBUSTION AND VENTILATION
WARNING: This heater shall not
be installed in a confined space or
unusually tight construction unless
provisions are provided for adequate
combustion and ventilation air. Read
the following instructions to insure
proper fresh air for this and other
fuel-burning appliances in your home.
PROVIDING ADEQUATE
VENTILATION
The following are excerpts from
National Fuel Gas Code, NFPA54/
A N S Z 2 2 3 . 1 . S e c t i o n 5 . 3 , A i r f o r
Combustion and Ventilation.
All spaces in homes fall into one of
the three following ventilation
classifications:
1. Unusually Tight Construction
2. Unconfined Space
3. Confined Space
The information on pages 4 through 6
will help you classify your space and
provide adequate ventilation.
Confined and Unconfined Space
The National Fuel Gas Code, ANS
Z223.1 defines a confined space as a
space whose volume is less than 50
cubic feet per 1,000 Btu per hour
(4.8 m
3
per kw) of the aggregate
input rating of all appliances installed
in that space and an unconfining
space as a space whose volume is
not less than 50 cubic feet per 1,000
Btu per hour (4.8 m
3
per kw) of the
aggregate input rating of all appli-
ances 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.
This heater shall not be installed in
a confined space or unusually tight
construction unless provisions are
provided for adequate combustion
and ventilation air.
* Adjoining rooms are communicating
only if there are doorless passage-
ways or ventilation grills between
them.
Unusually Tight Construction
DETERMINING FRESH AIR FLOW FOR HEATER LOCATION
Determining if You Have a Confined or Unconfined Space
Use this worksheet to determine if you have a confined or unconfined space.
Space: Includes the room in which you will install heater plus any adjoining rooms with doorless passageways
or ventilation grills between the rooms.
1. Determine the volume of the space (length
×
width
×
height).
Length
×
Width
×
Height= cu.ft. (volume of space)
Example: Space size 20 ft. (length)
×
16 ft.( width)
×
8 ft. (ceiling height)=2560 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. Divide the space volume by 50 cubic feet to determine the maximum Btu/Hr the space can support.
(volume of space)
÷
50 cu. ft.=(Maximum Btu/Hr the space can support)
Example: 2560 cu. ft. (volume of space)
÷
50 cu.ft.=51.2 or 51,200(maximum Btu/Hr the space can support)
The air that leaks around doors and
windows may provide enough fresh
air for combustion and ventilation.
However, in buildings of unusually tight
c o n s t r u c t i o n , y o u m u s t p r o v i d e
additional fresh air.
Unusually tight construction is defined
as construction where:
a) walls and ceilings exposed to the
outside atmosphere have a
continuous water vapor retarder
with a rating of one perm ( 6
×
10
-11
kg
p e r p a - s e c - m
2
) o r l e s s w i t h
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.
If your home meets all of the three
criteria above, you must provide
additional fresh air. See Ventilation Air
From Outdoors, page 5.
If your home does not meet all of the
three criteria above, proceed to
Determining Fresh Air Flow For
Heater Location, below.
