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119162-01H
7
AIR FOR COMbUSTION AND VENTILATION
Continued
Confined and Unconfined Space
The National Fuel Gas Code, ANSI Z223.1/
NFPA 54
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.ag-
gregate.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 hour (4.8 m
3
.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 un
-
confined space.
*.Adjoining.rooms.are.communicating.only.if.
there.are.doorless.passageways.or.ventilation.
grills.between.them.
DETERMINING FRESH-AIR FLOW
FOR HEATER LOCATION
Determining if You Have a Confined or
Unconfined Space
Use.this.work.sheet.to.determine.if.you.have.
a confined or unconfined space.
Space:
Includes.the.room.in.which.you.will.install.
fireplace plus any adjoining rooms with door
-
less.passageways.or.ventilation.grills.between.
the.rooms.
1.. Determine.the.volume.of.the.space.(length.
x.width.x.height).
.
Length.x.Width.x.Height.=__________cu..ft..
(volume.of.space)
.
Example:
Space size 20 ft. (length) x 16 ft.
(width).x.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.. Multiply.the.space.volume.by.20.to.determine.
the.maximum.Btu/Hr.the.space.can.support.
.
. ________ (volume.of.space).x.20.=.(Maxi-
mum.Btu/Hr.the.space.can.support)
.
Example:
.2560.cu..ft..(volume.of.space).x.20.
= 51,200 (maximum Btu/Hr the space can
support)
3.. Add.the.Btu/Hr.of.all.fuel.burning.appliances.
in.the.space.
Vent-free fireplace
.__________ Btu/Hr
Gas water heater*
.__________ Btu/Hr
Gas furnace
.__________ Btu/Hr
.
Vented.gas.heater.
.__________ Btu/Hr
Gas fireplace logs
.__________ Btu/Hr
.
Other.gas.appliances*.+._________ Btu/Hr
.
Total..
=._________ Btu/Hr
.
*.Do.not.include.direct-vent.gas.appliances..
Direct-vent. draws. combustion. air. from. the.
outdoors.and.vents.to.the.outdoors.
.
Example:
.
Gas water heater
.__________ Btu/Hr
Vent-free fireplace
+
._________ Btu/Hr
.
Total.
=._________ Btu/Hr
.. Compare. the. maximum. Btu/Hr. the. space.
can.support.with.the.actual.amount.of.Btu/Hr.
used.
.
._______Btu/Hr.(max..the.space.can.support).
.
.______ Btu/Hr.(actual.amount.of.Btu/Hr.used)
.
Example:
51,200 Btu/Hr (maximum the
space.can.support).
73,000 Btu/Hr (actual amount of
Btu/Hr.used)
The space in the above example is a confined
space.because.the.actual.Btu/Hr.used.is.more.
than. the. maximum. Btu/Hr. the. space. can. sup-
port..You.must.provide.additional.fresh.air..Your.
options.are.as.follows:
A. Rework worksheet, adding the space of an
adjoining.room..If.the.extra.space.provides.
an unconfined space, remove door to adjoin
-
ing. room. or. add. ventilation. grills. between.
rooms.. See.
Ventilation Air From Inside
Building,
page.8
.
B.. Vent. room. directly. to. the. outdoors.. See.
Ventilation Air From Outdoors,
page.8.
C. Install a lower Btu/Hr fireplace, if lower Btu/Hr
size makes room unconfined.
If.the.actual.Btu/Hr.used.is.less.than.the.maxi-
mum Btu/Hr the space can support,
the.space.is.
an unconfined space. You will need no additional
fresh.air.ventilation.
WARNING: If the area in
which the heater may be oper
-
ated 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/NFPA 54, Air for
Combustion and Ventilation,
or
applicable local codes.
40,000
33,000
73,000