Giant
Manual
15
When
communica ng
indirectly
with
the
outdoors
through
ver cal
ducts,
each
opening
shall
have
a
minimum
free
area
of
1
in
2
/4,000
BTU/hr
(550
mm
2
/kW)
of
total
input
ra ng
of
all
appliances
in
the
con
fi
ned
space.
Combus on
air
to
the
appliance
can
be
provided
from
a
well
ven lated
a c
or
crawl
space.
Combus
Ɵ
on Air Requirements
Using Outdoor Air For Combus
Ɵ
on
Outdoor
air
can
be
provided
to
a
con
fi
ned
space
through
two
permanent
openings,
one
commencing
within
12
in.
(300
mm)
of
the
top
and
one
commencing
within
12”
(300
mm)
of
the
bo om,
of
the
con
fi
ned
space.
The
openings
shall
communicate
to
the
outside
by
one
of
two
ways:
When
communica ng
directly
with
the
outdoors
through
horizontal
ducts,
each
opening
shall
have
a
minimum
free
area
of
1
in
2
/2,000
BTU/hr
(1,100
mm
2
/kW)
of
total
input
ra ng
of
all
appliances
in
the
con
fi
ned
space.
Note:
If
ducts
are
used,
the
cross
sec onal
area
of
the
duct
must
be
greater
than
or
equal
to
the
re
‐
quired
free
area
of
the
openings
to
which
they
are
connected.
Using Indoor Air For Combus
Ɵ
on
When
using
air
from
other
room(s)
in
the
building,
the
total
volume
of
the
room(s)
must
be
of
adequate
volume
(Greater
than
50
cubic
feet
per
1,000
BTU/hr).
Each
Combus on
air
opening
must
have
at least one square inch
(6.45 cm
2
) of free area for each 1,000 BTU/hr
,
but
not
less
than
100
square
inches
(645
cm
2
)
each.
Directly through horizontal ducts
Indirectly through ver
Ɵ
cal ducts
