Page 36 - 2018_IMC

DEFINITIONS

space or spaces to be heated or cooled (see also “Return air Type L vent. A vent listed and labeled for use with the
system”). following:
THEORETICAL AIR. The exact amount of air required to 1. Oil-burning appliances that are listed for use with
supply oxygen for complete combustion of a given quantity Type L vents.
of a specific fuel. 2. Gas-fired appliances that are listed for use with
THERMAL RESISTANCE (R). A measure of the ability to Type B vents.
retard the flow of heat. The R-value is the reciprocal of ther- VENT CONNECTOR. The pipe that connects an approved
mal conductance. fuel-fired appliance to a vent.
[P] THIRD-PARTY CERTIFICATION AGENCY. An VENT DAMPER DEVICE, AUTOMATIC. A device
approved agency operating a product or material certification intended for installation in the venting system, in the outlet of
system that incorporates initial product testing, assessment an individual automatically operated fuel-burning appliance
and surveillance of a manufacturer’s quality control system. that is designed to open the venting system automatically
when the appliance is in operation and to close off the vent-
[P] THIRD-PARTY CERTIFIED. Certification obtained ing system automatically when the appliance is in a standby
by the manufacturer indicating that the function and perfor- or shutdown condition.
mance characteristics of a product or material have been
determined by testing and ongoing surveillance by an VENTILATION. The natural or mechanical process of sup-
approved third-party certification agency. Assertion of certi- plying conditioned or unconditioned air to, or removing such
fication is in the form of identification in accordance with the air from, any space.
requirements of the third-party certification agency. VENTILATION AIR. That portion of supply air that comes
from the outside (outdoors), plus any recirculated air that has
[P] THIRD-PARTY TESTED. Procedure by which an
approved testing laboratory provides documentation that a been treated to maintain the desired quality of air within a
product, material or system conforms to specified require- designated space.
ments. [FG] VENTING SYSTEM. A continuous open passageway
TLV-TWA (THRESHOLD LIMIT VALUE-TIME- from the flue collar of an appliance to the outdoor atmo-
WEIGHTED AVERAGE). The time-weighted average con- sphere for the purpose of removing flue or vent gases. A vent-
ing system is usually composed of a vent or a chimney and
centration of a refrigerant or other chemical in air for a nor- vent connector, if used, assembled to form the open passage-
mal 8-hour workday and a 40-hour workweek, to which way.
nearly all workers are repeatedly exposed, day after day,
without adverse effects, as adopted by the American Confer- WATER HEATER. Any heating appliance or equipment
ence of Government Industrial Hygienists (ACGIH). that heats potable water and supplies such water to the pota-
ble hot water distribution system.
TOILET ROOM. A room containing a water closet and, fre-
quently, a lavatory, but not a bathtub, shower, spa or similar ZONE. One occupiable space or several occupiable spaces
bathing fixture. with similar occupancy classification (see Table 403.3.1.1),
occupant density, zone air distribution effectiveness and zone
TOXICITY CLASSIFICATION. Refrigerants shall be primary airflow rate per unit area.
classified for toxicity in one of two classes in accordance
with ASHRAE 34:
Class A. Refrigerants that have an occupational exposure
limit (OEL) of 400 parts per million (ppm) or greater.
Class B. Refrigerants that have an OEL of less than 400
ppm.
TRANSITION FITTINGS, PLASTIC TO STEEL. An
adapter for joining plastic pipe to steel pipe. The purpose of
this fitting is to provide a permanent, pressure-tight connec-
tion between two materials that cannot be joined directly one
to another.
[FG] UNIT HEATER. A self-contained appliance of the fan
type, designed for the delivery of warm air directly into the
space in which the appliance is located.
VENT. A pipe or other conduit composed of factory-made
components, containing a passageway for conveying combus-
tion products and air to the atmosphere, listed and labeled for
use with a specific type or class of appliance.
Pellet vent. A vent listed and labeled for use with listed
pellet-fuel-burning appliances.

2018 INTERNATIONAL MECHANICAL CODE  19
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