USG Casting Fireplace Surrounds - Manual (Page 28)

Alpha Gypsum
Specially processed calcium sulfate
hemihydrate.
ANSI (American National
Standards Institute)
A nonprofit, national technical asso-
ciation that publishes standards
covering definitions, test methods,
recommended practices and speci-
fications of materials. Formerly
American Standards Assn. (ASA)
and United States of America
Standards Institute (USASI).
BTU (British Thermal Unit)
The primary heat measurement unit
used by the hearth industry, this is
the amount of heat required to raise
the temperature of 1 lb. of water by
1 °F at sea level.
Calcine
The process of heating a mineral to
produce a change in its chemical
structure.
Calcined Gypsum
A dry powder; primarily calcium
sulfate hemihydrate, resulting from
calcination of gypsum; cementitious
base for production of most gypsum
plasters: also called plaster of Paris;
sometimes called stucco.
Carbon Monoxide
A practically odorless toxic com-
bustible gas formed in incomplete
combustion. At moderate levels,
symptoms include severe head-
aches, dizziness, mental confusion,
nausea, or feeling faint.
Caryatid
A sculptured female figure used as
an ornamental support in place of
a column or pilaster, often flanking
a doorway or as a decorative detail
around a fireplace.
Catalytic
Catalytic wood stoves and fireplace
inserts have ceramic honeycombed
chambers coated with a metal cata-
lyst (usually platinum or palladium)
that increases the rate of combus-
tion. The catalytic combustor burns
away gases and particulates nor-
mally emitted into the air. Catalytic
wood stoves allow the burning of
wood at lower temperatures for
longer periods of time.
Chimney
A portion of the venting system
through which flue gases are vented
to the outdoors and by which pene-
trated combustible surfaces are
protected; a primarily vertical shaft
enclosing at least one flue, the design
of which results in a natural draft.
Circulating Firebox
A firebox with louvers at the top
and bottom so that a fan can be
installed.
Circulating Fireplace
A fireplace with multiple-wall con-
struction around the fire chamber
that permits air to circulate between
the walls, become heated, and enter
the house directly or via short ducts.
Clearance
The air-space distance required
by building and fire codes between
firebox, stove, smoke pipe or
chimney and combustible materials
such as wood furniture or carpets.
Clearances must be observed even
if noncombustible plaster or other
masonry materials protect the
combustible materials.
Consistency
A term denoting the fluidity or vis-
cosity of a plaster or cementitious
paste; also refers to the amount
of water required to bring a given
quantity of dry cementitious mater-
ial and aggregate to a given fluidity.
Decorative Gas Appliance
in a Vented Fireplace
A self-contained, freestanding fuel
gas burning appliance designed
for installation only in a vented fire-
place, with a primarily aesthetic
function. Gas hearth appliances
which are listed to ANSI Standard
Z21.60 include gas log sets.
Direct Vent
An appliance that draws combus-
tion air from outdoors and exhausts
its combustion products to the out-
doors, eliminating the need for a
standard chimney system. The glass
panel in direct vent units is critical
to keeping the combustion system
sealed from the home, maintaining
high efficiency and indoor air quality.
Factory-Built Fireplace
Prefabricated metal fire chamber and
its chimney, commonly called zero
clearance. Consists of listed manu-
factured components that are assem-
bled to form the completed fireplace.
Glossary
28 Casting Fireplace Surrounds