Safety Valve: A device that limits fluid (liquid and gaseous) pressures by discharging some of the pressurized liquid or gas.
Safety Relief Valve: An automatic pressure relieving device actuated by the static pressure upstream of the device, which opens in proportion to the increase in pressure over the opening pressure.
Salinity: Of, characteristic of, or containing common salt, or sodium chloride; salty.
Sampling Program: A field measurement study during which data is collected through samples and analyzed.
Sanitary Landfill: A landfill operated in accordance with applicable regulations to maintain sanitary conditions.
Sanitizer: One of three groups of antimicrobials registered by EPA for public health uses. EPA considers an anti-microbial to be a sanitizer when it reduces but does not necessarily eliminate all the microorganisms on a treated surface. To be a registered sanitizer, the test results for a product must show a reduction of at least 99.9% in the number of each test microorganism over the parallel control.
Saturated Air: Moist air in which the partial pressure of water vapour equals the vapour pressure of water at the existing temperature. This occurs when dry air and saturated water vapour coexist at the same dr -bulb temperature.
Saturated Air Vapor Mixture: Is one in which the space occupied by the mixture is saturated with water vapor at the mixture temperature.
Saturated Temperature: Of a fluid, the boiling point corresponding to a given pressure; evaporation temperature, condensation temperature.
Saturated Vapor Pressure: The pressure existing at a given temperature in a closed vessel containing a liquid and the vapor from that liquid after equilibrium conditions have been reached. It is dependent only on temperature and must be determined experimentally.
Saturated Zone: (a) An underground zone in which all openings in and between natural geologic materials are filled with water. (b) The zone in which the voids in the rock or soil are filled with water at a pressure greater than atmospheric. The water table is the top of the saturated zone in an unconfined aquifer.
Saturation Pressure: The saturation pressure for a pure substance for any given temperature is that pressure at which vapour and liquid, or vapour and solid, can coexist in stable equilibrium.
Saturation Ratio: The ratio of the specific humidity of humid air to that of saturated air at the same temperature and pressure, usually expressed as a percentage .
Savings-to-Investment Ratio (SIR): They are computed over the lifetimes of the retrofit measures installed and expressed in terms of the net present value of the retail cost of the dwelling's fuel. Under some methodologies, other benefits, etc. Investment usally takes into account materials, labor, and support costs. SIRs of greater than one are counted as cost effective under this DOE WAP method of determining cost-effectiveness.
Schedule of Compliance: A schedule of remedial measures including an enforceable sequence of actions or operations leading to compliance with an effluent limitation, other limitation prohibition or standard.
Schnitzler syndrome: Pronunciation (shnitz′lĕr). Tense, generalized chronic urticaria, joint or bone pain, and monoclonal gammopathy of kappa type.
Scrubber: An air pollution device that uses a spray of water or reactant or a dry process to trap pollutants in emissions.
SCUBA: Self Contained Underwater Breathing Apparatus.
Sea Level: This is the average level of the ocean over the entire earth. Tidal fluctuation is taken into account when determining sea level.
Sealants: Flexible materials used on the inside of a building to seal gaps in the building envelope thereby preventing uncontrolled air infiltration and exfiltration.
Sealed Combustion Heater: A heater that draws air for combustion from outdoors and has a sealed exhaust system.
Seals: Devices used between rotating and stationary parts to separate, and minimized leakage between, areas of unequal pressures.
Seasonal Efficiency: Refers to the overall efficiency of the central heating system including on and off cycle fuel utilization and heat loss. The calculation
of these factors is represented in the Annual Fuel Utilization Efficiency (AFUE) rating for the appliance. Distribution system loss is not factored into the AFUE.
Seasonal Energy Efficiency Ratio (SEER): A measure of seasonal or annual efficiency of a central air conditioner or air conditioning heat pump. It takes into account the variations in temperature that can occur within a season and is the average number of Btu of cooling delivered for every watt-hour of electricity used by the heat pump over a cooling season.
Seasonal Performance Factor (SPF): Ratio of useful energy output of a device to the energy input, averaged over an entire heating season.
Seasonal Performance Factor (SPF): Ratio of useful energy output of a device to the energy input, averaged over an entire heating season.
Seat: The stationary seating surface, the inlet of a valve.
Secondary Containment: A structure designed to capture spills or leaks, as from a container or tank. For containers and aboveground tanks, it is usually a bermed area of coated concrete. For underground tanks, it may be a second, outer, wall or a vault. Construction of such containment must meet certain requirements, and periodic inspections are required.
Second Law of Thermodynamics: Heat cannot, of itself, pass from a colder to a hotter body.
Secondary Standard: A pollution limit based on environmental effects such as damage to property, plants, visibility, etc. Secondary standards are set for criteria air pollutants.
Secondary Treatment: The treatment of wastewater by biological methods usually preceded by primary sedimentation. Secondary treatment removes from 80 to 95 percent of suspended matter and BOD.
Sediment: The soil, sand and minerals at the bottom of surface waters, such as streams, lakes and rivers. The term may also refer to solids that settle out of any liquid.
Sedimentary Rocks: Sedimentary rocks have their origins in the bottom of oceans, lakes, rivers and swamps such as was found millions of years ago when the plants and animals that eventually would become petroleum were deposited.
SEER: Acronym for Seasonal Energy Efficiency Ratio. This is the measurement used to rate the efficiency for a cooling system that can also be used for heating (i.e. containing a heat pump. The higher the SEER, the more efficient the system.
SEET: Seasonal Extreme Environmental Test — Trane facility that simulates series of rigorous tests to ensure the quality/reliability of outdoor units.
Selective Coating: Finishes applied to materials to improve their performance in relation to radiation of different wavelengths: for example those applied to solar absorbers would seek to have a high absorptance of solar radiation and a low emittance of long-wave (thermal) radiation, while those for glazing have a high transmittance to solar radiation and high reflectance of long wavelengths.
Selective surface (absorber): A surface absorbing essentially all incident solar radiation (short wave high temperature source), while emitting a small fraction of thermal radiation (long wave low temperature source).
Self-Contained System: Similar to a package unit where all components are contained within on cabinet. Portable and window air conditioners are examples of such systems.
Semantic Differential: A technique for obtaining a value for subjective response in which the subject is asked to denote the intensity of a stimulus by choosing a subdivision between two extremes.
Semi-enclosed Sunspace: A sunspace that shares common walls with the associated building.
Semi-Solid Waste: Waste containing less than 50 percent solids.
Semi-volatile Compounds (SVOCs): Chemical compounds containing carbon that evaporate readily, though not as readily as volatile organic compounds. SVOCs include naphthalene and phenol.
Sensible Heat: Heat which is associated with a change in temperature in contrast to a heat interchange associated with a change of state (latent heat).
Sensitive Groups: Identifiable subsets of the general population that are at greater risk than the general population to the toxic effects of a specific air pollutant (e.g., infants, asthmatics, elderly).
Sensitivity Date: Date that express the dependence of the heating performance of a passive solar heating system on individual parameters of the system design.
Separate Living Quarters: Living quarters in which the occupants do not live and eat with any other persons in the structure and that have either a direct access from the outside of the building or through a common hall or complete kitchen facilities for the exclusive use of the occupants. The occupants maybe a single family, one person living alone, two or more families living together, or any other group of related or unrelated persons who share living arrangements.
Septage: Waste (water and solids) pumped from a septic tank.
Septic System: See disposal system.
Septic Tank: A large volume, water-tight tank that provides initial treatment of wastewater.
Sequence: The order in which compressors are brought online.
Sequencer: A bimetal switch that turns on the elements of an electric furnace in sequence.
Sequestration: A term that is used to refer to the uptake of CO2 from the atmosphere by plants and its subsequent storage as biomass.
Setback Thermostat: A thermostat that can be set to automatically lower temperatures in an unoccupied house and raise them again before the occupant returns.
Settleable Solids (SS): Solids in suspension that will settle under quiescent conditions.
Settling: This term refers to the effect of insulation depressing over time and, thereby, reducing the overall energy efficiency of the materials. This process is primarily the result of using too much air when installing the blown-in insulation - commonly called "fluffing," or the effect of long periods of time on the materials. One reason to re-inspect some work several months after installation to assess the settling factor. Settling can also occur during the installation of sidewall insulation when the cavity is not completely filled. This is usually avoided if "dense pack" protocols are followed during the installation.
Sewage Treatment: Treating wastewater in three stages: (1.) primary treatment – first state which refers to the settling/floating out of large suspended solids by screening and sedimentation before either discharging the treated wastewater or subjecting it to further treatment; (2.) secondary treatment-additional treatment by biological processes to break down organic matter remaining in the sewage following primary treatment; and (3.) tertiary treatment additional treatment of sewage beyond the secondary state to accomplish a very high degree of pollution reduction. Typical pollutants removed are organic chemicals, nutrients and excessive salts. Typically, primary treatment is physical, secondary treatment is biological and tertiary treatment is chemical and/or physical.
Shading Coefficient (SC): A decimal describing how much solar energy is transmitted through a window opening compared to clear single glass having an SC of 1.0. For example, reflective glass has an SC of .20 to .45.
Shaft: The part of the rotating element on which the rotating parts are mounted and by means of which energy is transmitted from the prime mover.
Shaft Input: The power required at the compressor drive shaft. Losses in external transmissions such as gears and belt drives are not included.
Shaft Sleeves: Devices that may be used to position the impeller or to protect the shaft.
Shaft Speed Irregularity: The dimensionless number obtained when the difference between maximum and minimum instantaneous shaft speeds during one period is divided by the arithmetic mean of these two.
Sheathing: A structural sheeting, attached on top of the framing, underneath siding, or on the roof of a building.
Sheeting: Common term for any building material used for covering a building surface.
Shell: The building's exterior envelope including walls, floor, and roof.
Shellfish: Organisms identified by the California Department of Health Services as shellfish for public health purposes (i.e., mussels, clams and oysters).
Shingle: A modular roofing material, usually asphalt, that is installed in overlapping rows to cover the entire roof.
Short Circuit: A dangerous malfunction in an electrical circuit where electricity is flowing through conductors and into the ground without going through an electric load, like a light or motor.
Short-Circuiting: Situation that occurs when the supply air flows to return or exhaust grilles before entering the breathing zone (area of a room where people are). To avoid short-circuiting, the supply air must be delivered at a temperature and velocity that results in mixing throughout the space.
Sick Building Syndrome (SBS): Term that refers to a set of symptoms that affect some number of building occupants during the time they spend in the building and diminish or go away during periods when they leave the building. Cannot be traced to specific pollutants or sources within the building.
Sidewall Insulation: The process of installing insulation material, usually blown cellulose, into the non-insulated wall stud cavities of a structure to reduce heat loss. Installation is achieved by drilling one or more rows of holes into the wall, one in each stud cavity. To achieve the most effective results, a dense pack protocol is used to install "high density" insulation materials. The "packing" of the materials should be tight enough that the installer cannot move the insulation when complete. It is common to install materials at 3.5 pounds per square foot.
Significant: A statistically significant difference in the means of two distributions of sampling results at the 95 percent confidence level.
Silica Gel: A desiccant most commonly used in heat regenerative type dryers.
Sill: The bottom of a window or door frame.
Sill Box: The outer area of the floor bound by the rim joist, floor joist, sill plate, and floor.
Silviculture: The art of cultivating a forest or forestry.
Single Acting: The piston only compresses air with its stroke in one direction.
Single Stage Compressors: Machines in which air or gas is compressed in each cylinder or casing from initial intake pressure to final discharge pressure.
Sinusitis: Inflammation of a sinus membrane, especially in the nasal region.
SIP Credit: The permanent, measurable emission benefits that are accounted for in a State Implementation Plan.
Siphon Feed Gun: Any paint gun which uses air flowing over an opening to create a vacuum to draw paint up a tube to be atomized.
SI Units (Systeme International d'Unites): The International System of Units being adopted throughout the world.
Skin Temperature: The average temperature of the skin surface.
Skin Wettedness: A theoretical measure of the coverage of the skin by sweat needed to explain the rate of evaporation of sweat as a proportion of the total skin surface area.
Skylight: Horizontal or sloping window in the ceiling of a room.
Sleeve: A type of journal bearing in centrifugal air compressors.
Sling Psychrometer: Device holding two thermometers that is slung through the air to measure relative humidity.
Slip: Is the internal leakage within a rotary compressor. It represents gas at least partially compressed but not delivered. It is experimentally determined and expressed in CFM to be deducted from the displacement to obtain capacity.
Slip RPM: Is the speed required of a rotary compressor to maintain a given discharge pressure, supplying leakage only (zero actual output). It is an experience factor.
Slough: A slowly moving shallow marsh.
Sludge: Residual solids and semi-solids from the treatment of water, wastewater, and other liquids.
Slurry Wall: Barriers used to contain the flow of contaminated groundwater or subsurface liquids. Slurry walls are constructed by digging a trench around a contaminated area and filling the trench with any material that tends not to allow water to pass through it. The groundwater or contaminated liquids trapped within the area surrounded by the slurry wall can be extracted and treated.
Slusher: An air operated device for hoisting or pulling. Similar to a winch.
Small Hydro: In addition to very large hydro plants in the West, the United States has many smaller hydro plants. Like large plants, small-scale hydroelectric systems capture the energy in flowing water and convert it to electricity. Although the potential for small hydroelectric systems depends on the availability of suitable water flow, these systems can provide cheap, clean, reliable electricity where the resource exists.
Smog: A mixture of pollutants, principally ground-level ozone, produced by chemical reactions in the air involving smog-forming chemicals. A major portion of smog-formers comes from burning of petroleum-based fuels such as gasoline. Other smog-formers, volatile organic compounds, are found in products such as paints and solvents. Smog can harm health, damage the environment and cause poor visibility. Major smog occurrences are often linked to heavy motor vehicle traffic, sunshine, high temperatures and calm winds or temperature inversion (weather condition in which warm air is trapped close to the ground instead of rising). Smog is often worse away from the source of the smog-forming chemicals, since the chemical reactions that result in smog occur in the sky while the reacting chemicals are being blown away from their sources by winds.
Smog Check Program: (See Inspection and Maintenance Program).
Smoke: A form of air pollution consisting primarily of particulate matter (i.e., particles released by combustion). Other components of smoke include gaseous air pollutants such as hydrocarbons, oxides of nitrogen, and carbon monoxide. Sources of smoke may include fossil fuel combustion, agricultural burning, and other combustion processes.
Softwood: A soft tree species with less density and energy per piece of wood than hardwood. (E.g. Pine, Spruce, Fir, Balsam, Hemlock...)
Soffit: The underside of a roof overhang or a small lowered ceiling, as above cabinets or a bathtub.
Soil Borings: Soil samples taken by drilling a hole in the ground.
Soil Gas: The gas present in soil which may contain radon.
Soil-Gas-Retarder: A continuous membrane or other comparable material used to retard the flow of soil gases into a building.
Sol-air Temperature: The hypothetical temperature which would give the same temperature distribution and heat flow in a building element that would result from the impact of the actual combination of the absorbed short wave radiation, long wave exchange with sky and ground, forced convection due to wind at the given external air temperature . It is used to assess transfer of heat through a specific building element of a given surface color. Different sol-air temperatures are encountered on differently orientated surfaces for materials of the same surface properties.
Solar Absorptance: The fraction of incident solar radiation that is absorbed upon striking a surface.
Solar Aperture: That portion of the solar wall covered by glazing.
Solar Collection Area: The projected area of a collector normal to the direction of the sun.
Solar Collector: A device for capturing solar energy, ranging from ordinary windows to complex mechanical devices. See also flat plate collector, focusing collector.
Solar Constant: The irradiance of solar radiation beyond the earth's atmosphere at the average earth-sun distance on a surface perpendicular to the sun's rays. The value for the solar constant is 1.353 kW/m2.
Solar Fraction (or percentage solar): The percentage of the total heat load supplied by the solar heating system, including useful losses from the storage.
Solar Gain: Heat from the sun, entering a room through transparent surfaces (kW/m2).
Solar Heat: Radiant energy from the sun with wavelengths between 0.7 and 1 micrometers.
Solar Heat Gain: In passive solar heating a term referring to the amount of heat gained through windows over the heating season. Net solar gain refers to the solar heat gain less the heat losses through the windows (kWh/m2).
Solar Heat Gain Coefficient (SHGC): The ratio of solar heat gain through a window to incident solar heat, including both transmitted heat and absorbed/radiated heat.
Solar Heat Gain Factor (SHGF): Solar heat gain amount on a surface with a particular angle and orientation expressed in Btus per square foot per hour.
Solar Load Ratio (SLR): Ratio of solar gain to building load used in SLR correlations.
Solar Radiation: Radiation emitted by the sun, including infrared radiation, visible light and ultraviolet radiation.
Solar Savings Fraction (SSF): The ratio of the solar savings to the energy requirement of the reference nonsolar building.
Solar Spectrum: The radiation emitted by the sun outside the atmosphere approximates to that emitted by a black body at 6000oK. At the surface of the earth, the majority of the radiation falls within a range of wavelengths from 300 to 2,500 nm and typically about ha1f the energy comes in the form of visible light (380 to 700 nm wavelength). Ultra violet radiation has wavelengths shorter than 380 nm and only forms a very small proportion of the spectrum. Due to water vapour and carbon dioxide and other absorbing gases in the atmosphere, several bands of long wave radiation are substantially removed.
Solar Time: A time scale based on the movement of the sun, such that noon is when the sun is at the highest of its arc and is true south, as opposed to local standard time.
Solar Transmittance: The percent of total solar energy transmitted by a material.
Sole Plate: A metallic pad, usually embedded in concrete, on which the compressor feet are mounted.
Solenoid: A magnetic device that moves a switch or valve stem.
Solid State: One of three states of matter characterized by stability of dimensions, relative incompressibility, and molecular motion held to limited oscillation. [Note the term solid state is often used to talk about solid-state semiconductors].
Solid Waste - Any garbage, refuse, sludge from treatment facilities, and other discarded material (including solid, liquid and contained gaseous material) resulting from industrial, commercial, mining and agricultural operations and from community activities. Sewage and certain other wastes are exempted.
Solution Gas: Natural gas that is dissolved in the crude oil within the reservoir and is released to the atmosphere when the crude oil is pumped to the surface.
Solvent: A liquid capable of dissolving another substance to form a solution. Water is sometimes called “the universal solvent” because it dissolves so many things, although often to only a very small extent. Organic solvents are used in paints, varnishes, lacquers, industrial cleaners and printing inks, for example. The use of such solvents in coatings and cleaners has declined over the last several years, because the most common ones are toxic, contribute to air pollution and may be fire hazards.
Solvent Base: Hydrocarbon- containing compounds such as paint thinner used for the purpose of thinning various types of coatings such as paint.
Soot: Very fine carbon particles that have a black appearance when emitted into the air.
Sound Insulation: The ability of building elements to reduce the sound level between internal spaces, or between outdoors and indoors. In HVAC systems: acoustical treatment of fan housings, supply ducts, space enclosures, and other parts of system and equipment to isolate vibration or to reduce noise transmission.
Source: Any place or object from which pollutants are released. A source can be a power plant, factory, dry cleaning business, gas station or farm. Cars, trucks and other motor vehicles are sources, and consumer products and machines used in industry can be sources too. Sources that stay in one place are referred to as stationary sources; sources that move around, such as cars or planes, are called mobile sources.
Space Heating: Heating the living spaces of the home with a room heater or central heating system.
Span: Horizontal distance between supports.
SPC: Specific Power Consumption.
Specific Energy Requirement: The shaft input per unit of compressor capacity.
Specific Fuel Consumption: The ratio of fuel consumption to compressor capacity.
Specific Gravity: This property is the ratio of the specific weight of air or gas to that of dry air at the same pressure and temperature.
Specific Heat: The amount of heat required to raise the temperature of a unit mass of any substance one degree as a fraction of that required to raise the temperature of unit mass of a standard substance one degree (usually water at 15oC).
Specific Heat Capacity: A measure amount of energy required to raise a unit mass or volume of a material through a unit temperature change. (kWh/kg.K, J/kg.K. kWh/m3.K, J/m3.K).
Specific Humidity: The weight of water vapor in an air-vapor mixture per pound of dry air.
Specific Power: A measure of air compressor efficiency, usually in the form of bhp/100 acfm or acfm/bhp.
Specific Volume: The volume of a substance per unit mass; the reciprocal of density.
Specific Weight: This property of a gas is the weight of air or gas per unit volume. Unless specified, it refers in compressor practice to the weight per unit volume at conditions of total temperature, total pressure and composition which prevail at the compressor intake.
Spectrum (of radiation): Display or specification of the components of the radiation considered in terms of intensity and wavelength. (Notes: (l) there are line spectra, where the spectrum consists of a finite number of 'lines' at particular wavelength(s) and continuous spectra where there is an infinite number of wavelengths with no sudden discontinuities of intensity. Some spectra exhibiting both these characteristics. (2) this term is also used for spectral efficiencies [excitation spectrum, action spectrum].
Specular Reflectance: Proportion of incoming radiation which undergoes specular reflection.
Specular Reflection: Reflection at a surface where the angle of reflection (more or less) equals the angle of incidence (as happens in a mirror).
Specular Surface: A surface with specular reflection properties. For example finishes such as polished aluminum, stainless steel or tin.
Speed: The number of revolutions per minute of the compressor shaft.
Spherical Irradiance, Radiant Fluence Rate (at a point): Quantity defined by the formula
 where d_ is the solid angle of each elementary beam passing through the given point and Le its radiance at that point. (Unit: W/m2).
Spillage: Temporary flow of combustion gases from a dilution device.
Spindle: The rod connecting the disc to the lever on a valve.
Spline: A strip of vinyl, rubber, or plastic that, when inserted into a groove, holds a screen or plastic film in place on a frame.Spherical irradiance, radiant fluence rate (at a point): quantity defined by the formula where d_ is the solid angle of each elementary beam passing through the given point and Le its radiance at that point. (Unit: W/m2).
Split-System: This is an air conditioner that has been split into two units. The outdoor unit contains the condenser and compressor, the indoor unit contains the evaporator coil.
Split-System Air Conditioner: Air conditioner having the condenser and compressor outdoors and the evaporator indoors.
Spoils: Loose rock, solid and vegetation debris left from construction or mining activities.
Spray Pond: Arrangement for lowering the temperature of water in contact with outside air by evaporative cooling of the water. The water to be cooled is sprayed by nozzles into the space above a body of previously cooled water and allowed to fall by gravity into it.
SRM: Screw compressor development center. Licensor to 90% of twin screw compressor market.
Stability: Stability is 100 minus the surge limit at rated discharge pressure, where the surge limit is expressed in percentage of rated capacity.
Stack: A chimney, smokestack, or vertical pipe that discharges used air.
Stack Effect: The tendency of air or gas in a duct or other vertical passage to rise when heated due to its lower density in comparison with that the surrounding air or gas. In buildings, the tendency towards displacement (caused by an increase in temperature) of internal heated air by unheated outside air, due to the difference in density of outside and inside air. See Convective.
Stack Up: The interaction between the stages of a centrifugal compressor. When a multi-stage compressor is designed, each stage can operate at only one point its characteristic curve. The point is determined by the design conditions of temperature, flow and pressure. As the design conditions change the point on the stage characteristic curve will shift. The interaction of each stage curve is referred to as the “stack up” of the compressor.
Stages: Steps in the compression of a gas, In reciprocating compressors, each stage usually requires a separate cylinder, in dynamic compressors, each requires a separate rotor disc.
Stagnation: Occurs when part of the room does not benefit from the fresh supply air or
in a room that does not have any ventilation.
Stakeholder: Any person or group who directly or indirectly affects, is affected by or has an interest in the actions of the State and Regional Water Boards.
Standard: See Water Quality Standard.
Standard Air: Dry air at a pressure of 101.325 kPa at a temperature of 20oC. The density is than 1.2041 kg/m3.
Standard Air Density: Air having a density of approximately 1.201 Kg/m³ (0.075 lb/ft³); that is, standard air with a specific volume of 0.832 m³/kg (13.33 ft ³/lb).
Standard Conditions: A set of physical, chemical or other parameters of a substance or system which defines an accepted reference state or forms a basis for comparison.
Standing Loss: Heat loss from a hot water storage tank through its shell.
Start Stop Control (SPT): A system in which air supply is matched to demand by the starting and stopping of the unit.
State: Of a system (or part thereof) is its condition at an instant of time as described or measured by its properties.
State Implementation Plan (SIP): A detailed description of the programs a state will use to carry out its responsibilities under the Clean Air Act. State implementation plans are collections of the regulations used by a state to reduce air pollution in non-attainment areas. The Clean Air Act requires that EPA approve each state implementation plan. Members of the public are given opportunities to participate in review and approval of state implementation plans.
Static Pressure: Condition that exists when an equal amount of air is supplied to and exhausted from a space. At static pressure, equilibrium has been reached.
Stationary Source: A place or object from which pollutants are released and which does not move around. Stationary sources include power plants, gas stations, incinerators, houses etc.
State Mussel Watch Program (SMW): Monitors toxic pollutant levels in resident and transplanted California mussels from coastal, bay and estuarine areas.
Steady Conditions: An operating state of a system, including its surroundings, in which the extent of change with time of all the significant parameters is so small that no important effects on the performance can be observed or measured.
Steady-state Model (of thermal comfort): A theoretical model of thermal response based on climate chamber measurements in conditions which are held constant in time.
Stem: The rod connecting the disc to the lever on a valve.
Sterile Air: Free from living organisms and especially micro-organisms. Usually used in food and dairy applications.
Sterilization: The destruction of all living organisms in water or on the surface of various materials. In contrast, disinfection is the destruction of most living organisms.
Sterilizer: One of three groups of antimicrobials registered by EPA for public health uses. EPA considers an antimicrobial to be a sterilizer when it destroys or eliminates all forms of bacteria, fungi, viruses, and their spores. Because spores are considered the most difficult form of a microorganism to destroy, EPA considers the term sporicide to be synonymous with “sterilizer.”
Stratosphere: Part of the atmosphere, the gases that encircle the Earth. The stratosphere is a layer of the atmosphere 9 to 31 miles above the Earth. Ozone in the stratosphere filters out harmful sun rays, including a type of sunlight called ultraviolet B, which has been linked to health and environmental damage.
Steady State Efficiency: The measurement of heat system balance in the on-cycle when heat into system equals heat out. Generally provided as a percentage of the maximum available heat generation capacity (100%) against the amount of usable heat being sent to the distribution system. This figure can also represent the percentage of heat being used within the system as compared to the heat lost through the flue. The reading is most valid when the stack temperature becomes constant and the distribution pumps or blowers are operating.
Steam Electric Plant (Conventional): A plant in which the prime mover is a steam turbine. The steam used to drive the turbine is produced in a boiler where fossil fuels are burned.
Steam Trap: An automatic valve that closes to trap steam in a radiator until it condenses.
Steam Vent: A bimetal-operated air vent that allows air to leave steam piping and radiators, but closes when steam strikes the surface.
Sterilizer: One of three groups of antimicrobials registered by EPA for public health uses. EPA considers an antimicrobial to be a sterilizer when it destroys or eliminates all forms of bacteria, fungi, viruses, and their spores. Because spores are considered the most difficult form of a microorganism to destroy, EPA considers the term sporicide to be synonymous with "sterilizer."
Stock Pond: A pond, having a capacity of 10 acre-feet or less, which is used primarily for watering livestock.
Stonewall: The unstable operation of a centrifugal compressor below the design point of the compressor.
Stop: A thin, trim board for windows and doors to close against or slide against.
Storm Water: Storm water runoff, snow melt runoff and surface run off and drainage.
STP: Standard pressure and temperature. See standard air.
Strainer: A device used to separate air solids from the stream of air that might become a source of trouble. Adulterants caught in the strainer are blown out through an orifice fitted with a valve or plug. The strainer should be opened periodically for a thorough cleaning.
Stratosphere: Part of the atmosphere, the gases that encircle the Earth. The stratosphere is a layer of the atmosphere 9-31 miles above the Earth. Ozone in the stratosphere filters out harmful sun rays, including a type of sunlight called ultraviolet B, which has been linked to health and environmental damage.
Strike Plate: The metal plate attached to the door jamb that the latch inserts into upon closing.
Stroke Total: The difference between the maximum extended height and the compressed height of an air actuator.
Stroke Usable: That part of the total stroke which can be utilized repeatedly in actuator applications. It is measured starting at the compressed height and is the difference between the compressed height and the actuator height limit.
Stud: A vertical wood or metal framing member used to build a wall.
Sub bituminous Coal: Sub bituminous coal, or black lignite, is dull black and generally contains 20 to 30 percent moisture. The heat content of sub bituminous coal ranges from 16 to 24 million Btu per ton as received and averages about 18 million Btu per ton. Sub bituminous coal, mined in the western coal fields, is used for generating electricity and space heating.
Sub-Floor: The sheathing over the floor joists and under the floor covering.
Subheaders: Are the connections between the headers and the work station.
Subject: A person taking part in a comfort survey.
Subject Population: A group of people who form the basis for a comfort survey.
Subject Sample: A sample of the subject population who participate in the survey.
Subjective Response: The sensation caused by a physical stimulus (generally a comfort vote).
Sub-Slab Depressurization System (Active): A system designed to achieve lower sub-slab air pressure relative to indoor air pressure by use of a fan-powered vent drawing air from beneath the slab.
Sub-Slab Depressurization System (Passive): A system designed to achieve lower sub-slab air pressure relative to indoor air pressure by use of a vent pipe routed through the conditioned space of a building and connecting the sub-slab area with outdoor air, thereby relying solely on the convective flow of air upward in the vent to draw air from beneath the slab.
Sub-Membrane Depressurization System: A system designed to achieve lower sub-membrane air pressure relative to crawlspace air pressure by use of a fan-powered vent drawing air from under the soil-gas-retarder membrane.
Suction Pressure: This is the pressure found on the suction side of a refrigeration system.
Sulfates: (See Sulfur Oxides.)
Sulfur Dioxide: A criteria air pollutant and gas produced by burning coal, most notably in power plants. Some industrial processes, such as production of paper and smelting of metals, produce sulfur dioxide. Sulfur dioxide is closely related to sulfuric acid, a strong acid. Sulfur dioxide plays an important role in the production of acid rain.Sump: A pit or tank that catches liquid runoff for drainage or disposal.
Sulfur Oxides: Pungent, colorless gases (sulfates are solids) formed primarily by the combustion of sulfur-containing fossil fuels, especially coal and oil. Considered major air pollutants, sulfur oxides may impact human health and damage vegetation.
Sulphur: One of the elements present in varying quantities in coal which contributes to environmental degradation when coal is burned. In terms of sulphur content by weight, coal is generally classified as low (less than or equal to 1 percent), medium (greater than 1 percent and less than or equal to 3 percent), and high (greater than 3 percent). Sulphur content is measured as a percent by weight of coal on an "as received" or a "dry" (moisture-free, usually part of a laboratory analysis) basis.
Sun Effect: Solar energy transmitted into interior spaces through windows and building materials.
Sun tempered Building: A minimal solar building derived from a conventional building by orienting its long axis east-west and placing a substantial fraction of its window area on the south side.
Sunlight: Visible part of direct solar radiation. (Note: when dealing with actinic effect of optical radiations, this term is commonly used for radiations extending beyond the visible region of the spectrum.)
Sunshine (possible percentage): The actual number of hours of sunshine expressed as a percentage of the maximum possible duration for the month (or other period).
Sunshine Duration [S]: Sum of time intervals within a given time period (hour, day, month, year) during which the irradiance from direct solar radiation on an plane normal to the sun direction is equal to or greater that 200 W/m2.
Sunspace: See attached sunspace or semi-enclosed sunspace.
Supercompressibility Factor: This is a factor expressing deviation of a gas from perfect gas laws.
Superfund: (a) State and federal funding mechanisms and programs to clean up hazardous waste sites that pose a threat to public health, (enacted in 1976). (b) Comprehensive Environmental Response, Compensation and Liability Act of 1980 (CERCLA).
Supply Air: Air that has been heated or cooled and is moved through the ducts and to the supply registers of a home.
Surface Cooling: Method used to cool air or other gas by passing it over cold surfaces.
Surface Film Conductance: The rate of heat flow per unit area under steady conditions between a surface and a fluid for unit temperature difference between the surface and fluid [in W/m2.K].
Surface Filtration: Filtration that occurs at the surface layer (as opposed to within the body depth) of the filter, and is accomplished by passing the material to be filtered over a grating, screen, sieve or membrane fabric with micro sized holes. The size of the holes in the filter determines what materials will pass through and which materials will be retained by the filter.
Surface Impoundment: A waste management unit which is a natural topographic depression, excavation or diked area, and which is designed to contain liquid wastes or wastes containing free liquids and which is not an injection well.
Surface Resistance: With the transition from air to material and material to air a surface resistance has to be overcome. It has two components, the surface resistance for convection/conduction Rc whose value depends on the rate of air flow over the surface and radiative surface resistance for long wave radiation heat transfer Rr whose value depends on the surface emittance and the surface temperature.
Surge: Is the reversal of flow within a dynamic compressor that takes place when the capacity being handled is reduced to a point where insufficient pressure is being generated to maintain flow. Also known as pumping.
Surge Limit: In a dynamic compressor, surge limit is the capacity below which the compressor operation becomes unstable.
Surge Tanks: A tank used to absorb irregularities in flow of liquids, including liquid waste materials, so that the flow out of the tank is constant.
Surveillance: Constant observation of a place or process.
Suspended Solids: The small, solid particles in water or wastewater that cause a cloudy condition. Solids that either float on the surface of, or are in suspension in water or wastewater which are removable by filtering.
Survey (comfort survey, field survey): An experimental investigation of subjective responses of a group of subjects in the field, generally assumed to be undertaken in such a way as to disrupt the normal pattern of the subject's lives as little as possible, and to leave subjects to decide their own dress and activity, use of environmental controls and so on.
Suspended Ceiling: Modular ceiling panels supported by a hanging frame.
Sweat Rate: The rate at which sweat is produced by the body.
Swept Volume: Term mainly used by companies selling small compressors because it makes their compressors look bigger than they really are. The swept volume is the actual displacement of the piston, forgetting such losses as bumping clearances, valve clearances, ring losses and the like. It’s not unusual to see an advertisement offering a compressor with (say) a delivery of 30 cfm, swept. In reality the compressor will only deliver about 20 scfm.
Synthetic Lubricant: A lubricating oil made with synthetic base stocks.
System (Electric): Physically connected generation, transmission, and distribution facilities operated as an integrated unit under one central management, or operating supervision.
Systematic Errors: Errors in the underlying assumptions of a theoretical comfort model which are temperature-dependent, and will therefore give rise to errors in its predictions.
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