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GLOSSARY ‘S’
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. 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 SYNDROME: "SBS" If more than 20 percent of the building occupants complain of such problems as headache, eye irritation, fatique 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) SILICA GEL: A regenerative absorbent consisting of the amorphous silica manufactured by the action of HCl on sodium silicate. Hard, glossy, quartzlike 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. 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. 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. 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. 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 airstream 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. 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. 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. 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. SUN EFFECT: Solar energy transmitted into space through windows and building materials. 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. 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. 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.
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