A B C D E F G H I J K L M N O P Q R S T U V W X Y Z
SABIN: The unit of acoustic absorption. One sabin
is one square foot of perfect sound-absorbing
material.
SAPROPHYTE: Any organism that requires and utilizes
preformed nutrients from dead or decaying organisms.
SEALANT: the adhesive or other material that
creates a leak proof seal between the filter pack
and the filter frame.
SEMIVOLATILE ORGANIC COMPOUND (SVOC): one of
them subset of volatile organic compounds that
may be found in gas or solid form at room temperature
and pressure. Indoor SVOCs include many pesticide
compounds, polychlorinated biphenyls, and polycyclic
aromatic hydrocarbons.
SENSIBLE HEAT: Heat that can be measured by a
thermometer; the heat which can raise the temperature
of a substance, as opposed to latent heat.
SENSOR: A device which detects or measures sensible
heat.
SET POINT: The value of the controlled condition
at which the instrument is set to operate. The
set point in the example in "differential"
might be 69 1/2o, the mid point of the differential.
SHORT-TERM EXPOSURE LIMIT (STEL): ACGIH-recommended
exposure limit. Maximum concentration to which
workers can be exposed for a short period of time
(15 minutes) for only four times throughout the
day with at least one hour between exposures.
SICK BUILDING: a building in which the indoor
air quality is considered to be unacceptable to
a substantial proportion of occupants.
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SICK BUILDING SYNDROME: “SBS” If more
than 20 percent of the building occupants complain
of such problems as headache, eye irritation,
fatigue and dizziness for more than two weeks;
if the symptoms are relieved when the complainant
leaves the building; and, if no specific cause
of the problem can be identified. (ASHRAE Journal,
July 1988, p.40)
SIDESTREAM SMOKE: the smoke that emerges from
the end of a cigarette between puffs by the smoker.
SILICA GEL: A regenerative absorbent consisting
of the amorphous silica manufactured by the action
of HCl on sodium silicate. Hard, glossy, quartz
like in appearance. Used in dehydrating and in
drying and as a catalyst carrier.
SINGLE ZONE: An HVAC system where one thermostat
controls the temperature of the entire building.
SINK: a material with the property of adsorbing
a chemical or pollutants with the potential of
subsequent reemission.
SINUSITIS: A swelling of one or more nasal sinuses.
It may be a complication of an upper respiratory
infection, dental infection, allergy a change
in atmosphere, as in air travel or underwater
swimming, or a defect of the nose. With swelling
of nasal mucous membranes the openings from sinuses
to the nose may be blocked, causing pressure,
pain, headache, fever, and local tenderness Complications
include spread of infection to bone, brain, ormeninges.
Treatment includes steam inhalations, nasal decongestants,
analgesics, and, if infection is present, antibiotics.
Surgery to improve drainage may be done to treat
chronic sinusitis.
SLIME LAYER: The gelatinous outermost covering
of certain bacteria; unlike capsules, which are
tightly bound to cell walls.
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SMOKE: An air suspension (aerosol) of particles,
originating from combustion or sublimination.
Carbon or soot particles less than 0.1 u in size
result from incomplete combustion of carbonaceous
materials such as coal or oil. Smoke generally
contains droplets as well as dry particles. Tobacco,
for instance, produces a wet smoke composed of
minute tarry droplets.
SORBENT: (1) A material that removes toxic gases
and vapors from air inhaled through a canister
or cartridge. (2) Material used to collect gases
and vapors during air-sampling.
SORE: 1. A wound, ulcer, or lesion. 2. Tender
or painful.
SOUND ABSORPTION COEFFICIENT: The ratio of the
sound energy absorbed by a surface of a medium
(or material) exposed to a sound field (or to
sound radiation), to the sound energy incident
on the surface.
SOURCE CONTROL: a preventive strategy for reducing
airborne contaminant levels through the removal
of the material or activity generating the pollutants.
SPECIFIC GRAVITY: The ratio of the mass of a unit
volume of a substance to the mass of the same
volume of a standard substance at a standard temperature.
Water at 4 C (39.2 F) is the standard usually
referred to for liquids; for gases, dry air (at
the same temperature and pressure as the gas)
is often taken as the standard substance. See
density.
SPECIFIC VOLUME: The reciprocal of density and
is used to determine the cubic feet of volume,
if the pounds of weight are known. Both density
and specific volume are affected by temperature
and pressure. The specific volume of air under
standard conditions is 13.33 cubic feet per pound
and the specific volume of water at standard conditions
is 0.016 cubic feet per pound.
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SPECIFIC WEIGHT: The weight per unit volume of
a substance, same as density.
SPECTROPHOTOMETER: An instrument used for comparing
the relative intensities of the corresponding
colors produced by chemical reactions.
SPREAD: The divergence of the air stream in a
horizontal or vertical plane after it leaves the
outlet.
SPORE: A resistant body formed by certain microorganisms;
resistant resting cells. Mold spores: unicellular
reproductive bodies.
STACHYBOTRYS ATRA: a rare toxigenic fungus species
that can produce tricothencenes, an extremely
potent variety of mycotoxin.
STACK EFFECT: a condition resulting from the
rise of heated air, which creates positive pressure
near the top of the building and negative pressure
toward the bottom. Stack effect pressures have
been known to overpower mechanical ventilation
systems, disrupting proper circulation and contributing
to the infiltration and stagnation of pollutants.
STAGNANT AIR AREA: An area within a space where
the air velocity is less than 25 fpm.
STANDARD AIR DENSITY: The density of air. 0.075
lb/cu ft (1.2 kg/m³), at standard conditions.
STATE: Refers to the form of a fluid, either
liquid, gas or solid. Liquids used in environmental
systems are water, thermal fluids such as ethylene
glycol solutions, and refrigerants in the liquid
state. Gases are steam, evaporated refrigerants
and the air-water vapor mixture found in the atmosphere.
Some substances, including commonly used refrigerants,
may exist in any of three states. A simple example
is water, which may be solid (ice), liquid (water),
or gas (steam or water vapor).
STATIC HEAD: The pressure due to the weight of
a fluid above the point of measurement.
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STATIC REGAIN METHOD: A method of duct sizing
wherein the duct velocities are systematically
reduced, allowing a portion of the velocity pressure
to convert to static pressure offsetting the duct
friction losses.
STATIC PRESSURE, SP: The pressure developed in
a duct by a fan; SP exerts influence in all directions;
the force in inches of water measured perpendicular
to flow at the wall of the duct; the difference
in pressure between atmospheric pressure and the
absolute pressure inside a duct, cleaner, or other
equipment.
STATISTICAL SIGNIFICANCE: the probability that
and degree to which the results of an experimental
study describe an actual relationship between
two factors beyond that which might be expected
by pure coincidence.
STEAM: Water vapor produced by heating water
to its boiling point and adding more heat; generally
considered to be at or above 212oF (100oC).
STEAM TRAP: A device used to keep the steam out
of the condensate line, while allowing the condensate
to go through the trap to the condensate line.
STERILIZE: To free from all forms of life.
STRATIFIED AIR: Unmixed air in a duct that is
in thermal layers that have temperature variations
of more than five degrees.
SUBCOOLING: The difference between the temperature
of a pure condensable fluid below saturation and
the temperature at the liquid saturated state,
at the same pressure.
SUBLIMATION: the conversion of a solid to a gas
without going through a liquid phase.
SUBMICROSCOPIC: not being visible through a compound
microscope, generally less than 0.1 m in diameter.
SUN EFFECT: Solar energy transmitted into space
through windows and building materials.
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SUPER COOLING: Cooling of a liquid to a temperature
below its condensing temperature.
SUPERHEAT: The difference between the temperature
of a pure condensable fluid above saturation and
the temperature at the dry saturated state, at
the same pressure.
SUPPLY: the ventilation system components involved
in providing ventilation air, as in supply vents,
supply ducts, supply diffusers.
SUPPLY AIR: a mixture of re-circulated air and
outside air that has been conditioned and delivered
to a space. Supply air can range from 100% re-circulated
air to 100% outside air.
SURFACE AREA (CARBON): the surface area of granular
activated carbon as determined by the BET method,
expresses in square meters per gram of carbon.
SYSTEM: A series of ducts, conduits, elbows,
branch piping, etc. designed to guide the flow
of air, gas or vapor to and from one or more locations.
A fan provides the necessary energy to overcome
the resistance to flow of the system and causes
air or gas flow through the system. Some components
of a typical system are louvers, grilles, diffusers,
filters, heating and cooling coils, air pollution
control devices, burner assemblies, volume flow
control dampers, mixing boxes, sound attenuators,
the ductwork and related fittings.
SYSTEM, CENTRAL FAN: A mechanical, indirect system
of heating, ventilating, or air conditioning,
in which the air is treated or handled by equipment
located outside the rooms served, usually at a
central location, and conveyed to and from the
rooms by means of a fan and a system of distributing
ducts.
SYSTEM, CLOSED: A heating or refrigerating piping
system in which circulating water or brine is
completely enclosed, under pressure above atmospheric,
and shut off from the atmosphere except for an
expansion tank.
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SYSTEM, DUCT: A series of ducts, conduits, elbows,
branch piping, etc. designed to guide the flow
of air, gas or vapor to and from one or more locations.
A fan provides the necessary energy to overcome
the resistance to flow of the system and causes
air or gas to flow through the system. Some components
of a typical system are louvers, grilles, diffusers,
filters, heating and cooling coils, energy recovery
devices, burner assemblies, volume dampers, mixing
boxes, sound attenuators, the ductwork and related
fittings.
SYSTEM, UNITARY: A complete, factory-assembled
and factory-tested refrigerating system comprising
one or more assemblies which may be shipped as
one unit or separately but which are designed
to be used together.
SYSTEM CURVE: A graphic presentation of the pressure
vs. volume flow rate characteristics of a particular
system.
SYSTEMIC EFFECTS: the physical effects that occur
following absorption of a given agent into the
body, manifesting at an organ or site removed
from the point of contact.
SYSTEMS CONTROL: the control of indoor air pollutants
through the use of mechanical means, i.e., through
ventilation control or air cleaning.
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