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ACGIH - American Conference of Governmental Industrial Hygienists; publishes guidebook Industrial Ventilation Manual, A manual of Recommended Practice.
ACID AEROSOL - Acidic liquid or solid particles that are small enough to become airborne. High concentrations of acid aerosols can be irritating to the lungs and have been associated with some respiratory diseases, such as asthma.
ACTION LEVEL - A term used to identify the level of indoor radon at which remedial action is recommended. (EPA's current action level is 4 pCi/L.)
ACTION PACKET - In reference to the IAQ Tools for Schools Action Kit - contains numerous products to assist school personnel to implement an effective yet simple IAQ program in their school.
AEROSOL - Particles (solid or liquid) that remain suspended in air for a period of time. Aerosols include mists, smokes, fumes, and dusts.
AHU - See "Air Handling Unit."
AIR = 0.075 pounds per cubic foot (1.2 kg/cubic meter)
AIR CHANGES PER HOUR - The number of times indoor air is theoretically replaced by outdoor air during an hour.
AIR CLEANER - A device to separate contaminants from an air stream. Examples include filters, scrubbers, electrostatic precipitators and cyclones.
AIR CLEANING - An IAQ control strategy to remove various airborne particulates and/or gases from the air. The three types of air cleaning most commonly used are particulate filtration, electrostatic precipitation, and gas sorption.
AIR EXCHANGE RATE - The rate at which outside air replaces indoor air in a space. Expressed in one of two ways: the number of changes of outside air per unit of time air changes per hour (ACH); or the rate at which a volume of outside air enters per unit of time - cubic feet per minute (cfm).
AIR HANDLING UNIT (AHU) - For purposes of this document refers to equipment that includes a blower or fan, heating and/or cooling coils, and related equipment such as controls, condensate drain pans, and AIR FILTERS. Does not include ductwork, registers or grilles, or boilers and chillers.
AIR HORSEPOWER (AHP) - The power required to move air through a ventilation system against a specific pressure.
AIR PASSAGES - Openings through or within walls, through floors and ceilings, and around chimney flues and plumbing chases, that permit air to move out of the conditioned spaces of the building.
AIR, STANDARD - Dry air [Oxygen (20.95% by volume), Nitrogen (78.09% by volume) Carbon dioxide (0.03% by volume)] at 700°F and 29.92 in (Hg) barometric pressure. This is substantially equivalent to 0.0757 lb/ft3. Specific heat of dry air = 0.24 btu/lb/F.
ALLERGEN - A substance capable of causing an allergic reaction because of an individual's sensitivity to that substance.
ALLERGIC RHINITIS - Inflammation of the mucous membranes in the nose that is caused by an allergic reaction.
ANEMOMETER - A device used to measure air velocity. Common types of anemometers include the rotating vane, the swinging vane, and the hot.
ANIMAL DANDER - Tiny scales of animal skin.
ANSI - American National Standards Institute; publishes consensus standards on ventilation, e.g. ANSI/AIHA Z9.7-1998 for Recirculation of Air.
ANTIMICROBIAL - Agent that kills microbial growth. See "disinfectant," "sanitizer," and "sterilizer."
ASHRAE - American Society of Heating, Refrigerating, and Air-Conditioning Engineers.
BASELINE - Measurements from the Local Exhaust Ventilation (LEV) duct network static pressures and airflow measurements that prove all points on the network are within design parameters. This is the reference point is where the system must be returned to when the network gets unbalanced. The information is recorded on the system drawing when the system is installed and started up.
BIOLOGICAL CONTAMINANTS - Agents derived from, or that are, living organisms (e.g., viruses, bacteria, fungi, and mammal and bird antigens) that can be inhaled and can cause many types of health effects including allergic reactions, respiratory disorders, hypersensitivity diseases, and infectious diseases. Also referred to as "microbiologicals" or "microbials." Read More...
BLAST GATE - A sliding sheet metal valve used in ducts to create additional pressure loss in the duct and restrict flow.
BRAKE HORSEPOWER (BHP) - The actual horsepower required to move air through a ventilation system against a fixed total pressure plus the losses in the fan.
BREATHING ZONE - Area of a room in which occupants breathe as they stand, sit, or lie down.
BRITISH THERMAL UNIT (BTU) - Any of several units of energy (heat) in the HVAC industry, each slightly more than 1 kJ. One BTU is the energy required to raise one pound of water one degree Fahrenheit, but the many different types of BTU are based on different interpretations of this “definition”. In the United States the power of HVAC systems (the rate of cooling and dehumidifying or heating) is sometimes expressed in BTU/hour instead of watts. Abbreviated BTU or Btu.
BUILDING ENVELOPE - Elements of the building, including all external building materials, windows, and walls, that enclose the internal space.
BUILDING-RELATED ILLNESS (BRI) - Diagnosable illness whose symptoms can be identified and whose cause can be directly attributed to airborne building pollutants (e.g., Legionnaire's disease, hypersensitivity pneumonitis). Also: A discrete, identifiable disease or illness that can be traced to a specific pollutant or source within a building. (Contrast with "Sick building syndrome").
CAPTURE VELOCITY - The air velocity required to capture suspended dusts or aerosols and draw them into an exhaust hood.
CARCINOGEN - A physical, chemical or biological agent that is capable of inducing cancer in humans or animals.
CEILING PLENUM: Space below the flooring and above the suspended ceiling that accommodates the mechanical and electrical equipment and that is used as part of the air distribution system. The space is kept under negative pressure.
CENTRAL AIR HANDLING UNIT (Central AHU) - This is the same as an Air Handling Unit, but serves more than one area.
CFM - Cubic feet per minute. The amount of air, in cubic feet, that flows through a given space in one minute. 1 CFM equals approximately 2 liters per second (l/s).
CHEMICAL SENSITIZATION - Evidence suggests that some people may develop health problems characterized by effects such as dizziness, eye and throat irritation, chest tightness, and nasal congestion that appear whenever they are exposed to certain chemicals. People may react to even trace amounts of chemicals to which they have become "sensitized."
CHILLER - A device that removes heat from a liquid via a vapor-compression or absorption refrigeration cycle. This cooled liquid flows through pipes in a building and passes through coils in air handlers, fan-coil units, or other systems, cooling and usually dehumidifying the air in the building. Chillers are of two types; air-cooled or water-cooled. Air-cooled chillers are usually outside and consist of condenser coils cooled by fan-driven air. Water-cooled chillers are usually inside a building, and heat from these chillers is carried by recirculating water to a heat sink such as an outdoor cooling tower.
CO - Carbon monoxide. Read More...
CO2 - Carbon dioxide.
COEFFICIENT OF ENTRY (CE) - The hood captures, contains, or receives contaminants generated at an emission source by converting static air pressure to velocity pressure. Coefficient of Entry (Ce) is a measure of the efficiency of a hood's ability to convert static pressure to velocity pressure.
COIL - Equipment that performs heat transfer to air when mounted inside an air handling unit or ductwork. It is heated or cooled by electrical means or by circulating liquid or steam within it.
COMBINATION FOUNDATIONS - Buildings constructed with more than one foundation type; e.g., basement/crawlspace or basement/slab-on-grade.
COMMISSIONING - Start-up of a building that includes testing and adjusting HVAC, electrical, plumbing, and other systems to assure proper functioning and adherence to design criteria. Commissioning also includes the instruction of building representatives in the use of the building systems.
CONDENSER - A component in the basic refrigeration cycle that ejects or removes heat from the system. The condenser is the hot side of an air conditioner or heat pump. Condensers are heat exchangers, and can transfer heat to air or to an intermediate fluid (such as water or an aqueous solution of ethylene glycol) to carry heat to a distant sink, such as ground (earth sink), a body of water, or air (as with cooling towers).
CONDITIONED AIR - Air that has been heated, cooled, humidified, or dehumidified to maintain an interior space within the "comfort zone." (Sometimes referred to as "tempered" air.)
CONFINED SPACE - An enclosure such as a storage tank, process vessel, boiler, silo, tank car, pipeline, tube, duct, sewer, underground utility vault, tunnel, or pit that has limited means of egress and poor natural ventilation and that may contain hazardous contaminants or be oxygen deficient.
CONSTANT AIR VOLUME (CAV) SYSTEMS - Air handling system that provides a constant air flow while varying the temperature to meet heating and cooling needs.
CONTAMINANT - A harmful, irritating, or nuisance material that is foreign to the normal atmosphere.
DAMPERS - Controls that vary airflow through an air outlet, inlet, or duct. A damper position may be immovable, manually adjustable or part of an automated control system.
DELTA T - A reference to a temperature difference. It is used to describe the difference in temperature of a heating or cooling fluid as it enters and as it leaves a system.
DENSITY - Density is the weight of a unit volume of a substance:
DIFFUSER - An air outlet; sometimes associated with an inlet air register; constructed of louvered or perforated metal plates to discharge and mix supply air with ambient room air.
DIFFUSERS AND GRILLES - Components of the ventilation system that distribute and return air to promote air circulation in the occupied space. As used in this document, supply air enters a space through a diffuser or vent and return air leaves a space through a grille.
DILUTION VENTILATION - A form of ventilation, which relies on mixing uncontaminated air with contaminated air in such quantities that the resultant mixture in the breathing zone will not exceed the allowable exposure limit specified for any contaminant.
DISINFECTANTS - One of three groups of antimicrobials registered by EPA for public health uses. EPA considers an antimicrobial to be a disinfectant when it destroys or irreversibly inactivates infectious or other undesirable organisms, but not necessarily their spores. EPA registers three types of disinfectant products based upon submitted efficacy data: limited, general or broad spectrum, and hospital disinfectant.
DRAIN TILE LOOP - A continuous length of drain tile or perforated pipe extending around all or part of the internal or external perimeter of a basement or crawlspace footing.
DRAIN TRAP - A dip in the drain pipe of sinks, toilets, floor drains, etc., which is designed to stay filled with water, thereby preventing sewer gases from escaping into the room.
DUCT - Specialized housing for the air flow.
DUST - Mechanically produced solid particles (e.g. from crushing, drilling, grinding, sweeping, or handling of solid materials).
ENTRY LOSS - The loss in static pressure caused by air flowing into a duct or hood. It is usually expressed in inches of water gauge.
ENVIRONMENTAL AGENTS - Conditions other than indoor air contaminants that cause stress, comfort, and/or health problems (e.g., humidity extremes, drafts, lack of air circulation, noise, and over-crowding).
ENVIRONMENTAL TOBACCO SMOKE (ETS) - Mixture of smoke from the burning end of a cigarette, pipe, or cigar and smoke exhaled by the smoker (also secondhand smoke (SHS) or passive smoking). Read More...
ERGONOMICS - Applied science that investigates the impact of people's physical environment on their health and comfort (e.g., determining the proper chair height for computer operators).
EVASE - A diffuser at the outlet that gradually increases in area to decrease velocity and to convert kinetic energy to static pressure at the outlet and inlet. It is used to ensure smooth and undisturbed airflow in and out of the fan. It converts kinetic energy into pressure energy.
EXHAUST VENTILATION - Mechanical removal of air from a portion of a building (e.g., piece of equipment, room, or general area).
FAN - A mechanical device which causes air movement.
FLAMMABLE LIQUID - A substance which meets the criterion for WHMIS Class B Division 2 flammable liquid (a flash point less than 37.8°C (100°F);
FLOW HOOD - Device that easily measures airflow quantity, typically up to 2,500 cfm.
FRICTION LOSS - The static pressure loss in a ventilation system due to friction between moving air and the duct wall; expressed as inches w.g. (water gauge) per 100 feet of duct.
FUME - Solid particles generated by condensation from the gaseous state, generally after volatilization from melted substance (e.g. welding), and often accompanied by a chemical reaction such as oxidation. Gases and vapours are not fumes.
FUNGI - Any of a group of parasitic lower plants that lack chlorophyll, including molds and mildews.
GAS - A substance that is in the gaseous state at room temperature and pressure.
GAS SORPTION - Devices used to reduce levels of airborne gaseous compounds by passing the air through materials that extract the gases. The performance of solid sorbents is dependent on the airflow rate, concentration of the pollutants, presence of other gases or vapors, and other factors.
General ventilation - Ventilation system designed to maintain an acceptable indoor air by mixing the contaminated indoor air with fresh outdoor air and by controlling the temperature and humidity of the indoor air.
GOVERNMENTAL - In the case of building codes, these are the State or local organizations/agencies responsible for building code enforcement.
GREEN BUILDINGS - The building industry is increasingly focused on making its buildings greener, which includes using healthier, less polluting and more resource-efficient practices. Indoor environmental quality (IEQ) refers to the quality of the air and environment inside buildings, based on pollutant concentrations and conditions that can affect the health, comfort and performance of occupants -- including temperature, relative humidity, light, sound and other factors. Good IEQ is an essential component of any building, especially a green building. Read More...
HAZARDOUS ATMOSPHERE - Any atmosphere that is oxygen-deficient or that contains a toxic or disease-producing contaminant. The atmosphere may or may not be IDLH (immediately dangerous to life or health).
HEPA - High-Efficiency Particulate Air Filter - A filter designed to remove 99.97% of specific type particulate material (0.3 micrometers in diameter) from air.
HOOD - A device designed to contain and/or capture aerosols and direct them to the exhaust duct network.
HUMIDIFIER FEVER - A respiratory illness caused by exposure to toxins from microorganisms found in wet or moist areas in humidifiers and air conditioners. Also called air conditioner or ventilation fever.
HVAC - Heating, ventilation, and air-conditioning system.
HYPERSENSITIVITY DISEASES - Diseases characterized by allergic responses to pollutants. The hypersensitivity diseases most clearly associated with indoor air quality are asthma, rhinitis, and hypersensitivity pneumonitis. Hypersensitivity pneumonitis is a rare but serious disease that involves progressive lung damage as long as there is exposure to the causative agent.
HYPERSENSITIVITY PNEUMONITIS - A group of respiratory diseases that cause inflammation of the lung (specifically granulomatous cells). Most forms of hypersensitivity pneumonitis are caused by the inhalation of organic dusts, including molds.
IAQ - Indoor air quality.
IAQ BACKGROUNDER - A component of the IAQ Tools for Schools Action Kit that provides a general introduction to IAQ issues, as well as IAQ program implementation information.
IAQ CHECKLIST - A component of the IAQ Tools for Schools Action Kit containing information and suggested easy-to-do activities for school staff to improve or maintain good indoor air quality. Each Activity Guide focuses on topic areas and actions that are targeted to particular school staff. The Checklists are to be completed by the staff and returned to the IAQ Coordinator as a record of activities completed and assistance as requested.
IAQ COORDINATOR - An individual at the school and/or school district level who provides leadership and coordination of IAQ activities.
IAQ MANAGEMENT PLAN - A component of the IAQ Tools for Schools Kit, specifically, a set of flexible and specific steps for preventing and resolving IAQ problems.
IAQ TEAM - People who have a direct impact on IAQ in the schools (school staff, administrators, school board members, students and parents) and who implement the IAQ Action Packets.
IDLH ATMOSPHERE - An atmosphere immediately dangerous to life or health (IDLH). An IDLH atmosphere poses an immediate hazard to life, such as being oxygen deficient (containing less than 19.5% oxygen), or produces an irreversible debilitating effect on health.
INCHES OF WATER, "INCH W.G." - A unit of pressure. One inch of water is equal to the pressure exerted by a column of water one inch (25.4mm) high. Atmospheric pressure at standard conditions is 407 inches w.g.
INDICATOR COMPOUNDS - Chemical compounds, such as carbon dioxide, whose presence at certain concentrations may be used to estimate certain building conditions (e.g., airflow, presence of sources).
INDOOR AIR POLLUTANT - Particles and dust, fibers, mists, bioaerosols, and gases or vapors.
INDUSTRIAL VENTILATION (IV) - The equipment or operation associated with the supply or exhaust of air, by natural or mechanical means, to control occupational hazards in the air in an industrial setting.
International Conference of Building Officials (Uniform Building Code/1991 and Uniform Mechanical Code/1991);
IPM: Integrated pest management.
LOCAL EXHAUST VENTILATION (LEV) - The mechanical removal of contaminated air from the point where the contaminant is being generated or liberated.
MAKE-UP AIR (ALSO KNOWN AS REPLACEMENT AIR) - Air supplied to a space to replace exhausted air.
MAKE-UP AIR - See "Outdoor Air Supply."
MANOMETER - An instrument that measures pressure; essentially it is an U-tube partially filled with liquid, usually water, mercury, or light oil. The difference in level of the liquid between the two sides of the tube indicates the pressure difference measured between the two sides of the U-tube.
MAP OF RADON ZONES - A U.S. EPA publication depicting areas of differing radon potential in both map form and in state specific booklets.
MCS - See "Multiple Chemical Sensitivity."
MECHANICALLY VENTILATED CRAWLSPACE SYSTEM - A system designed to increase ventilation within a crawlspace, achieve higher air pressure in the crawlspace relative to air pressure in the soil beneath the crawlspace, or achieve lower air pressure in the crawlspace relative to air pressure in the living spaces, by use of a fan.
MICROBIOLOGICALS - See "Biological Contaminants."
MINIMUM TRANSPORT VELOCITY - The minimum velocity which will transport particles in a duct with little settling (metric-m/s; U.S.-fpm).
MIST - An aerosol consisting of liquid particles generated by condensation of a substance from the gaseous to the liquid state.
MODEL BUILDING CODES - The building codes published by the 4 Model Code Organizations and commonly adopted by state or other jurisdictions to control local construction activity.
MULTIPLE CHEMICAL SENSITIVITY (MCS) - A condition in which a person reports sensitivity or intolerance (as distinct from "allergic") to a number of chemicals and other irritants at very low concentrations. There are different views among medical professionals about the existence, causes, diagnosis, and treatment of this condition.
NEGATIVE PRESSURE - Condition that exists when less air is supplied to a space than is exhausted from the space, so the air pressure within that space is less than that in surrounding areas. Under this condition, if an opening exists, air will flow from surrounding areas into the negatively pressurized space.
NFPA - National Fire Protection Association.
NIOSH - National Institute for Occupational Safety and Health.
NUISANCE DUST - Innocuous dust not causing a serious health condition.
ODOR THRESHOLD - The lowest concentration of an air contaminant that can be detected by smell.
ORGANIC COMPOUNDS - Chemicals that contain carbon. Volatile organic compounds vaporize at room temperature and pressure. They are found in many indoor sources, including many common household products and building materials.
OSHA - Occupational Safety and Health Administration - The U.S. Federal Agency that sets the minimum requirements for ventilation.
OUTDOOR AIR SUPPLY - Air brought into a building from the outdoors (often through the ventilation system) that has not been previously circulated through the system. Also known as "Make-Up Air."
OXYGEN DEFICIENCY - Concentration of oxygen in the ambient air of less than 19.5% by volume.
PARTICULATE MATTER - A suspension of fine solid or liquid particles in air such as dust, fog, fume, mist, smoke, or sprays. Particulate matter suspended in air is commonly known as an aerosol.
PEL - Permissible Exposure Limit as established by the Occupational Safety & Health Administration (OSHA).
PICOCURIE (pCi) - A unit for measuring radioactivity, often expressed as picocuries per liter (pCi/L) of air.
PLENUM - Air compartment connected to a duct or ducts.
PM - Preventive Maintenance.
POLLUTANT PATHWAYS - Avenues for distribution of pollutants in a building. HVAC systems are the primary pathways in most buildings; however all building components interact to affect how air movement distributes pollutants. Also - a term used in the IAQ Tools for Schools: IAQ Coordinator's Guide.
POSITIVE PRESSURE - Condition that exists when more air is supplied to a space than is exhausted, so the air pressure within that space is greater than that in surrounding areas. Under this condition, if an opening exists, air will flow from the positively pressurized space into surrounding areas.
PPM - Parts per million.
PRESSED WOOD PRODUCTS - A group of materials used in building and furniture construction that are made from wood veneers, particles, or fibers bonded together with an adhesive under heat and pressure.
PRESSURE DROP (DIFFERENTIAL PRESSURE, *P) - Pressure drop is a term used to characterize the reduction in air pressure between any two points in the ventilation duct network. The pressure drop occurs as the compressed air travels through filters and ducts. In airflow system, the energy is measured as "pressure drop."
PRESSURE, ABSOLUTE - The total pressure measured in relation to a perfect vacuum. The sum of atmospheric and gauge pressures.
PRESSURE, ATMOSPHERIC - The force exerted by the weight of the atmosphere on a given area. It is measured in units of pascals (Pa) or torr (millimetres of mercury). The normal atmospheric pressure is 760 torr or 101 kilopascals (kPa).
PRESSURE, GAUGE - Instruments used to measure pressure are called pressure gauges. Generally it gives air pressure relative to atmospheric pressure. It can show a negative pressure (less than atmosphere), or positive (greater than atmosphere.)
PRESSURE, STATIC (SP) - The potential pressure exerted by air at rest. Stated another way, it is the tendency of air to either burst or collapse a duct.
PRESSURE, STATIC - In flowing air, the total pressure minus velocity pressure. The portion of the pressure that pushes equally in all directions.
PRESSURE, TOTAL (TP) - The sum of the velocity pressure and static pressure of air in a duct.
PRESSURE, TOTAL - In flowing air, the sum of the static pressure and the velocity pressure.
PRESSURE, VELOCITY (VP) - The kinetic pressure (resulting from movement) in the direction of flow necessary to cause air to flow at a given velocity.
PRESSURE, VELOCITY - In flowing air, the pressure due to the velocity and density of the air.
PREVENTIVE MAINTENANCE - Regular and systematic inspection, cleaning, and replacement of worn parts, materials, and systems. Preventive maintenance helps to prevent parts, material, and systems failure by ensuring that parts, materials and systems are in good working order.
PSYCHOGENIC ILLNESS - This syndrome has been defined as a group of symptoms that develop in an individual (or a group of individuals in the same indoor environment) who are under some type of physical or emotional stress. This does not mean that individuals have a psychiatric disorder or that they are imagining symptoms.
PSYCHOSOCIAL FACTORS - Psychological, organizational, and personal stressors that could produce symptoms similar to those caused by poor indoor air quality.
RADIANT HEAT TRANSFER - Radiant heat transfer occurs when there is a large difference between the temperatures of two surfaces that are exposed to each other, but are not touching.
RADON (Rn) AND RADON DECAY PRODUCTS - Radon is a radioactive gas formed in the decay of uranium. The radon decay products (also called radon daughters or progeny) can be breathed into the lung where they continue to release radiation as they further decay.
RE-ENTRAINMENT - Situation that occurs when the air being exhausted from a building is immediately brought back into the system through the air intake and other openings in the building envelope.
RE-ENTRY - Situation that occurs when the air being exhausted from a building is immediately brought back into the system through the air intake and other openings in the building envelope.
RELs - Recommended Exposure Limits (recommendations made by the National Institute for Occupational Safety and Health (NIOSH)).
RETURN AIR - Air that is returned from the primary space to the fan for re-circulation.
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.
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. (Contrast with "Building related illness").
SLOT VELOCITY - Average velocity of air through a slot. It is calculated by dividing the total volume flow rate by the slot area.
SMOKE - Aerosols, gases, and vapours resulting from incomplete combustion.
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.
SOURCES - Sources of indoor air pollutants. Indoor air pollutants can originate within the building or be drawn in from outdoors. Common sources include people, room furnishings such as carpeting, photocopiers, art supplies, etc.
SPECIFIC GRAVITY - This is the ratio of the mass of a unit volume of a substance to the mass of the same volume of a standard substance. For example,
SPECIFIC GRAVITY OF AIR = 1.0 at sea level pressure and 68°F.
SPECIFIC GRAVITY OF WATER = 1.0 at 39.2°F.
STACK EFFECT - The overall upward movement of air inside a building that results from heated air rising and escaping through openings in the building super structure, thus causing an indoor pressure level lower than that in the soil gas beneath or surrounding the building foundation.
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.
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."
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.
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.
TEMPERED MAKEUP AIR - The make-up air that has been conditioned by heating or cooling to obtain a specific desired temperature.
TLV - Threshold Limit Value - A list published yearly by the American Conference of Governmental Industrial Hygienists (ACGIH) as a guide for exposure concentrations that a healthy individual normally can tolerate for eight hours a day, five days a week, without harmful effects. Airborne particulate concentrations are generally listed as milligrams per cubic meter of air (mg/m3). Gaseous concentrations are listed as parts per million (ppm) by volume.
TRACER GASES - Compounds, such as sulfur hexafluoride, which are used to identify suspected pollutant pathways and to quantify ventilation rates. Trace gases may be detected qualitatively by their odor or quantitatively by air monitoring equipment.
TROUBLESHOOTING - Evaluation of visual and measured data to determine action to restore a LEV to Baseline or reference condition.
TVOCs - Total volatile organic compounds. See "Volatile Organic Compounds (VOCs)"
UNIT VENTILATOR - A fan-coil unit package device for applications in which the use of outdoor- and return-air mixing is intended to satisfy tempering requirements and ventilation needs.
VAPOR - The gaseous state of a substance that is solid or liquid at room temperature and pressure.
VARIABLE AIR VOLUME SYSTEM (VAV) - Air handling system that conditions the air to constant temperature and varies the outside airflow to ensure thermal comfort.
VELOCITY PRESSURE - See Pressure, Velocity
VELOCITY, FACE - The speed at which air crosses the hood opening (metric-m/s; U.S.-fpm).
VENTILATION AIR - Defined as the total air, which is a combination of the air brought inside from outdoors and the air that is being re-circulated within the building. Sometimes, however, used in reference only to the air brought into the system from the outdoors; this document defines this air as "outdoor air ventilation."
VENTILATION RATE - The rate at which outdoor air enters and leaves a building. Expressed in one of two ways: the number of changes of outdoor air per unit of time (air changes per hour, or "ach") or the rate at which a volume of outdoor air enters per unit of time (cubic feet per minute, or "cfm").
VOLATILE ORGANIC COMPOUNDS (VOCs) - Compounds that vaporize (become a gas) at room temperature. Common sources which may emit VOCs into indoor air include housekeeping and maintenance products, and building and furnishing materials. In sufficient quantities, VOCs can cause eye, nose, and throat irritations, headaches, dizziness, visual disorders, memory impairment; some are known to cause cancer in animals; some are suspected of causing, or are known to cause, cancer in humans. At present, not much is known about what health effects occur at the levels of VOCs typically found in public and commercial buildings.
WATER = 62.3 pounds per cubic foot (1 kg/liter)
ZONE - The occupied space or group of spaces within a building which has its heating or cooling controlled by a single thermostat.
Glossary of Terms
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