4
FRESH AIR FOR
COMBUSTION AND
VENTILATION
PRODUCING ADEQUATE
VENTILATION
The following are excerpts from
National Fuel Gas Code. NFPA 54/
ANS Z223.1, Section 5.3. Air for
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.
WARNING: This heater
shall not be installed in a
confined space or unusually
t i g h t c o n s t r u c t i o n u n l e s s
provisions are provided for
adequate combustion and
v e n t i l a t i o n a i r . R e a d t h e
f o l l o w i n g i n s t r u c t i o n s t o
insure proper fresh air for this
and other fuel -burni ng
appliances in your home.
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
h o u r ( 4 . 8 m
3
p e r k w ) o f t h e
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
h o u r ( 4 . 8 m
3
p e r k w ) o f t h e
aggregate input rating of all
appliances installed in that space.
Rooms communicating directly with
t h e s p a c e i n w h i c h t h e
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
t i g h t c o n s t r u c t i o n u n l e s s
p r o v i s i o n s a r e p r o v i d e d f o r
adequate combustion and
ventilation air.
*
A d j o i n i n g r o o m s a r e
communicating only if there are
d o o r l e s s p a s s a g e w a y s o r
ventilation grills between them.
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, ANS Z223.1, Section 5.3
or applicable local codes.
Unusually Tight Construction
The air that leaks around doors and
windows may provide enough fresh
air for combustion and ventilation.
However, in buildings of unusually
tight construction, you must provide
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
per pa-sec-m
2
) 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. If your home meets
all of the three criteria above, you
must provide additional fresh air.
See Ventilation Air from Outdoors,
page 6.
If your home does not meet all of
the three criteria above, see
Determining Fresh-Air Flow for
Heater Location, page 5
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 20ft. (length)
×
16ft.( width)
×
8ft. (ceiling height)=2560cu. 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)
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