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Combustion
Air and Ventilation
for
Appliances
Located
in Unconfined
Spaces
UNCONFINED
SPACE
is space whose
volume
is not less than
50 cubic
feet per
1,000
Btu per hour
(4.8 m _ 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.
In unconfined
spaces
in buildings,
infiltration
may be adequate
to provide
air for combustion,
ventilation
and dilution
of flue
gases.
However,
in buildings
of tight construction
(for example,
weather
stripping,
heavily insulated,
caulked,
vapor barrier, etc.),
additional
air may
need
to be provided
using
the methods
described
in Combustion
Air
and
Ventilation
for Appliances
Located
in Confined
Spaces.
Combustion
Air and Ventilation
for
Appliances
Located
in Confined
Spaces
CONFINED
SPACE
is a space
whose
volume
is less
than
50 cubic
feet per 1,000
Btu per hour
(4.8 m s per kW)
of the
aggregate
input rating
of al! appliances
installed
in that space.
A. ALL AIR FROM INSIDE BUILDINGS:
(See Figure
9 on page
9 and Figure
10 below)
The
confined
space
shall
be provided
with
two
permanent
openings
communicating
directly
with
an additional
room(s)
of sufficient
volume
so that the combined
volume
of all spaces
meets
the criteria
for an unconfined
space.
The total input
of
al! gas
utilization
equipment
installed
in the combined
space
shall
be considered
in making
this
determination.
Each
opening
shall
have
a minimum
free
area
of one square
inch
per 1,000
Btu per hour (22 cm2/kW)
of the total input rating
ofal!
gas
utilization
equipment
in the confined
space,
but not less
than
100
square
inches
(845
cmZ).
One
opening
shall
commence
within
12 inches
(30
cm)
of the top
and
one
commencing
within
12 inches
(30 cm) of the bottom
of the
enclosures,
NT
bottom
of the enclosure.
The openings
shall
communicate
directly,
or by ducts, with the outdoors
or spaces
(craw! or attic)
that freely
communicate
with the outdoors.
ALT.
UNLET
AUR
VENTILATION
LOUVERS
FmGURE11.
When
directly communicating
with the outdoors,
each opening
shall have a minimum
free area of 1 square
inch per 4,000 Btu
per hour (5.5 cm_/kW) of total input rating of all equipment
in the
enc!osure.
See
Figure
12.
When
communicating
with
the outdoors
through
vertical
ducts,
each
opening
shall
have
a minimum
free
area
of
1 square
inch per 4,000
BTU per hour (5.5 cm_/kW)
of total
input
rating
of al!
equipment
in the
enclosure.
See
Figure
12.
CHIMNEY
OR GAS VENT
VENTILATION
LOUVERS
WATER
HEATER
FURNACE
nNLET AIR BUCT
ENDS 1' OR 30 cm
ABOVE
FLOOR)
FIGURE10.
B. ALLAIR
FROM
OUTDOORS:
(See Figures
9, 11,12 and 13)
The
confined
space
shall
be provided
with
two
permanent
openings,
one commencing
within
12 inches
(30 cm) of the
top and one commencing
within
12 inches
(30 cm) from
the
FIGURE 12.
When
communicating
with the outdoors
through
horizontal
ducts,
each
opening
shall
have
a minimum
free area
of 1
square
inch per 2,000
BTU per hour
(11 cm2/kW)
of total
input
rating
of al!
equipment
in the
enclosure.
See
Figure
13.
11
When
ducts
are used,
they
shall
be of the same
cross°
sectional
area
as the free
area
of the openings
to which
they
connect.
The
minimum
short
side
dimension
of
rectangular
air
ducts
shall
not
be less
than
3 inches
(76.2 ram).
See Figure
13.
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