I-Beam: A steel beam with a cross section resembling the letter “I.” It is used for long spans as basement beams or over wide wall openings, such as a double garage door, when wall and roof loads are imposed on the opening.

I-Joist: Manufactured structural building component resembling the letter “I.” Used as floor joists and rafters. I-joists include two key parts: flanges and webs. The flange of the I joist may be made of laminated veneer lumber or dimensional lumber, usually formed into a 1 ½” width. The web or center of the I-joist is commonly made of plywood or oriented strand board (OSB). Large holes can be cut in the web to accommodate duct work and plumbing waste lines. I-joists are available in lengths up to 60 feet long.

I / O RATIO (also I / E RATIO): Relative length of inspiration compared to expiration.

IAP:   Indoor air pollution.

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 Coordinator: An individual at the school and/or school district level who provides leadership and coordination of IAQ activities.

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 – Indoor Air Quality:  The quality of indoor air relative to its acceptability for healthful human habitation. Assessing and ameliorating, when necessary, the quality of indoor air is a major concern of the weatherization process. In particular, all by-products of major combustion appliances must be directly evacuated to the outdoors under all operating conditions.

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.

IARC:  International Agency for Research on Cancer: an international organization that conducts research on cancer and distributes information on different aspects of the subject.

IBV:  Inlet butterfly valve. These are fitted on the inlet of most types of compressor and the valve opens and closes to throttle the air flow. However, the term IBV is usually associated with turbo compressors.

ICCVAM:  ICCVAM, the Interagency Coordinating Committee on the Validation of Alternative Methods, is an agency of the US National Institute of Environmental Health Sciences (NIEHS), working to develop and validate new safety test methods, and to establish criteria and processes for the validation and regulatory acceptance of toxicological testing methods.

Ice Dam:  A mass of ice formed at the transition from a warm to a cold roof surface.  Frequently formed by re-freezing meltwater at the overhang of a sloping roof.  

Ice Melting Equivalent:  (IME-ICE MELTING EFFECT): Amount of heat absorbed by melting ice at 32 0F (0 0C1 is 144 Btu per pound of Ice or 288 000 Btu per ton ICFM:  CFM flowing through the compressor inlet filter or inlet valve under rated conditions.

ICM Motor:  Is a variable-speed motor. It adjusts its speed to deliver the right airflow needed by the system.

I.D.:  A measurement. Inside diameter.

IdealDefrost:  IdealDefrost is Carrier’s proprietary defrost management innovation for maintaining the ideal defrost interval for a heat pump, enhancing comfort and efficiency.

Ideal Gas:  Is a gas that follows the perfect gas laws without deviation. There is no such thing, however it is the basis from which calculations are made and corrections applied.

IdealHumidity:  IdealHumidity™ is Carrier’s proprietary humidity management innovation for maintaining the ideal comfort in a home.

Ideal Multi Stage Compression:  The condition when a perfect gas is isentropically compressed, and the gas inlet temperature and also the amount of work spent is the same for each stage.

Identification plate (Name Plate):  A plate mounted on the unit that Provides information such as manufacturer, part number and specifications.

Idler:  A pulley used on some belt drives to provide proper belt tension and to eliminate belt vibration.

(IDLH) Immediately Dangerous to Life or Health:  An atmosphere that poses an immediate threat to life, would cause irreversible adverse health effects, or would impair an individual's ability to escape from a dangerous atmosphere.

IDLH Atmosphere:  See Immediately Dangerous to Life or Health atmosphere.

I/E Ratio: Inhalation/exhalation ratio, or the relative length of inhalation (breathing in) compared to exhalation (breathing out).

IESNA (Illumination Engineering Society of North America):  The professional society of lighting engineers, including those from manufacturing companies and other professionally involved in lighting. It produces standard practice documents for applying proper lighting techniques to indoor and outdoor spaces.

IEST:  Institute of Environmental Sciences and Technology. The organization which historically sets standards for high efficiency air filters.

IGE (Immunoglobin E) Antibody: A special antibody released when the body is exposed to an allergen. Pokes holes in the immune system’s white cells, thus releasing chemicals, including histamine, which can trigger allergy symptoms.

Ignitable:   Capable of burning or causing a fire.

Ignite:  To heat a gaseous mixture to the temperature at which combustion takes place.

Ignition: The lighting of a fuel to make it burn.

Ignition Point:  The minimum temperature at which combustion of a solid or fluid can occur.

Ignition Source:  Anything that provides heat, spark or flame sufficient to cause combustion/explosion.

Ignition Temperature:  The minimum temperature to initiate or cause self-sustained combustion in the absence of any source of ignition.

Ignition Transformer:  Provides a high-voltage current, usually to produce a spark to ignite a furnace fuel, either gas or oil.

IGRA: Interferon gamma release assay. This is a type of blood test that detects cell-mediated immune response to this cytokine. In the U.S., QuantiFERON®-TB Gold is a
currently available IGRA.

IGV:  Inlet guide-vane valve. Valve assembly at the air inlet of a “blower” (single stage, low pressure, centrifugal air compressor). Usually advised to be mounted in very close proximity to the “blower” impeller. Provides “pre-swirl” of air flow in same rotational direction as “blower” impeller. Proven to improve efficiency (reduced bhp) during throttled-down modulation of “blowers.” Effectiveness, when used with multi-stage centrifugal air compressors, degrades rapidly.

IIC: A new system utilized in the Federal Housing Administration recommended criteria for impact sound insulation.

Illuminance (at a point of a surface): Quotient of the luminous flux dX incident on an element of the surface containing the point, by the area dA of that element. Equivalent definition. Integral, taken over the hemisphere visible at a given point, of the expression Lv.cosY.dX. where Ly. is the luminance at the given point in the various directions of the incident elementary beams of solid angle dX and Y is the angle between any of these beams and the normal to the surface at the given point.

Illumination: The light level measured on a horizontal plane in Foot Candles.

Immediately Dangerous to Life or Health atmosphere (IDLH Atmosphere):  An atmosphere that poses an immediate threat to life, would cause irreversible adverse health effects, or would impair an individual’s ability to escape.

Immiscible:  Incapable of being mixed without separation phases. Water and petroleum oil are immiscible under most conditions, although they can be made miscible with the addition of an emulsifier.

Immune System:  An intricate complex of interrelated cellular, molecular, and genetic components that provides a defense, the immune response, against foreign organisms or substances and aberrant native cells.

Immunization:  Vaccination or other process that induces protection (immunity) against infection or disease caused by a microbe.

Immunocompetent:  An animal whose immune system is functioning normally and capable of mounting an antibody or cell-mediated immune response, is immunocompetent.

Immunocompromised:  An animal whose immune system is not functioning normally and that may be incapable of mounting an antibody or cell-mediated immune response, is immunocompromised. Some genetic models are immune deficient (immunocompromised). Anti-rejection drugs also result in compromise of the immune system.

Immunoglobulins:  Proteins in the blood that are generated in reaction to foreign proteins or polysaccharides; also called “antibodies.” 

Immunosuppression:  Suppression of the natural immune response (see immunocompromised).

Immunotherapy:  Pronunciation (im′yū-nō-thār′ă-pē).  Originally, therapeutic administration of serum or immune globulin containing preformed antibodies produced by another individual. Currently, immunotherapy includes nonspecific systemic stimulation, adjuvant, active specific immunotherapy, and adoptive immunotherapy. New forms of immunotherapy include the use of monoclonal antibodies.  Syn: biologic immunotherapy.

Impact Analysis:  The second stage of life cycle assessment, in which the environmental impacts of a process, product, or facility are determined.

Impact Foil:  This is a feature exclusive to Miele Intensive Clean dustbags and is a piece of foil that is positioned opposite the dustbag opening that prevents sharp-edged objects, such as pine needles, glass and sand, from penetrating the bag while the vacuum cleaner is operating.  

Impact Resistance:  The ability of a protector to resist the force of an object that comes into contact with the lens or eye protector at the velocity specified in this standard.

Impaction:  Retention mechanism in gas filtration. Also called Inertial Collection and Inertial Impact. As the gas stream lines bed in the vicinity of the filter, the carried particles continue in a straight line due to their inertia and impact the filter. Effective primarily for particles about 0.3µm and larger, at high gas velocities and low filter porosity.

Impedance:  The resistance or opposition to airflow in a system. Same as back pressure or static pressure.

Impeller:  The part of the rotating element of a dynamic compressor that imparts energy to the flowing medium by means of centrifugal force. It consists of a number of blades mounted so as to rotate with the shaft.

Impeller Diameter: The maximum diameter measured over the impeller blade.

Impeller Humidifier:  A type of humidifier that produces a cool mist by means of a high speed rotating disk. Thought to produce large dispersions of both microorganisms and minerals.

Impermeable: Not permitting gas or water pass through.

Impervious:  Not allowing, or allowing only with great difficulty, the movement of water; impermeable.

Impingement:  The process in which particles are removed from an air stream because of their inertia. As air containing a particle flows toward a filter fiber or other collecting surface, the particle does not follow the air streamlines because of its inertia. Instead it moves in a straight line colliding with the filter fiber or surface to which it may become attached.

Impingement Filter:  Any filter which removes particulate only when the particles hit (impinge on) the filter media.

Impoundment:  A body of water or sludge confined by a dam, dike, floodgate or other barrier.

Improvement Analysis:  The third stage of life cycle assessment, in which design for environment techniques are used in combination with the results of the first and second LCA stages to improve the environmental plan of a process, product, or facility.

In Situ:  Refers to the treatment of contaminated areas in place without excavation or removal, as in the in situ treatment of on-site soils through biodegradation of contaminants.

In Vito:  In vitro measurements are synonymous with indirect bioassay techniques, such as plutonium urinalysis.

In Vivo:  In vivo measurements are synonymous with bioassay techniques, such whole body counting.

In-duct UVGI: The installation of ultraviolet germicidal irradiation (UVGI) lamps in a return or exhaust air duct to kill any M. tuberculosis that may be in the air stream.In-Kind Contributions:  In-kind contributions represent the value of non-cash contributions provided by the grantee, and non-Federal parties. In-kind contributions may be in the form of charges for real property and non-expendable personal property and the value of goods and services directly benefiting and specifically identifiable to the project or program.

In-Line Filter:  A filter assembly in which the inlet, outlet & filter element are in line.

In-place Leakage Test:  A system or bank test for leakage of filter units or charcoal adsorbers made after they are installed.

In-Situ: Sterilization or integrity testing of a filter in the system rather than as an ancillary operation such as in autoclave or bubble point stand.

In-Vitro:  In isolation from living organisms in an experimental artificial environment e.g. cells in tissue culture; experiments carried out in test tubes.

In-Vivo:  Within the living organism.

Incandescent Lamp: A lamp employing an electrically charged metal filament that glows at white heat. A typical light bulb.

Incentive Spirometer: A device that encourages deep inspiration to expand the lungs and improve cough effectiveness.
Inches of Mercury Column:  A unit used in measuring pressures. One inch of mercury column equals a pressure of 1.66 kPa (0.491 psi).

Inch of Water: Small air pressure differences caused by wind, blower doors, furnace fans, and chimneys are measured in inches of water (in.-H2O) in the American measurement system.

Inches of Water Column:  A unit used in measuring pressures. One inch of water column equals a pressure of 0.25 kPa (0.036 psi).

Inches of Water Gauge (w.g.):  A unit of measuring pressure or pressure differential (1 in. w.g. = 0.036 psi).

Incident Angle: In this context the angle between the beam of solar radiation and a line perpendicular (normal) to the irradiated surface

Incidental Disturbance:  The unintentional disturbance of, ACM, PACM, or asbestos material.

Incidental Disturbance Asbestos Project: The cleanup, repair or encapsulation of less than 10 square feet or less than 25 linear feet of incidentally disturbed ACM, PACM or asbestos material.

Incidental Repairs: Under DOE rules, this term refers to the repairs on a dwelling unit necessary for the effective performance or preservation of the allowable energy conservation measures to be installed. Usually, a specific dollar amount is set by a state to limit such incidental repairs.

Incineration: A treatment technology involving destruction of waste by controlled burning at high temperatures; e.g., burning sludge to remove the water and reduce the remaining residues to a safe, non-burnable ash that can be disposed of safely on land, in some waters, or in underground locations.

Inclined Manometer: A testing instrument using a liquid column, set at an incline to increase reading accuracy, to measure pressure. Normally used to read velocity pressure.
Incompatible:  Materials which could cause dangerous reactions from direct contact with one another.

Incompatibility: Descriptive of two or more materials which are not suitable to be used together.

Incremental Reactivity (IR): The additional ozone formed in the atmosphere with the incremental addition of a certain amount of a volatile organic compound .

Incubation Period:  A disease incubation period is the period of time between the actual infection and the first signs of disease.

Indemnification Clause: Provision in a contract in which one party agrees to be financially responsible for specified types of damages, claims, or losses.

Index: The interest rate or adjustment standard that determines the changes in monthly payments for an adjustable rate loan.

Index Patient: The first case who comes to attention as an indicator of a potential public
health problem.

Indicated Power:  Power as calculated from compressor-indicator diagrams.

Indication: Reason to use.

Indicator:  A species of plant, animal or bacterium whose presence is indicative of a particular environmental condition.

Indicator Card:  A pressure-volume diagram for a compressor or engine cylinder produced by direct measurement made by the use of a device called an indicator.

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).

Indicator Pressure:  An indicator that signals pressure conditions.

Indicator Species:  A species in a community or ecosystem that is more susceptible to disturbances than most other species.

Indigenous Materials:  Building with materials that are produced in an area near to where the construction is taking place. This reduces building costs
and helps to boost local economies.

Indirect Bioassay:  Measurements to determine the presence of and/or the amount of a radioactive material in the excreta, urine or in other biological materials removed from the body (synonymous with in vitro measurements).

Indirect Cooling: A system in which a liquid, such as brine or water, cooled by the refrigerant, is circulated to the material or space refrigerated or is used to cool air so circulated.

Indirect Gain: The indirect transfer of solar heat into the space to be heated from a collector that is coupled to the space by an uninsulated, conductive or convective medium (such as thermal storage wall or roof pond).

Indirect Lighting: Lighting achieved by reflection, usually from wall and/or ceiling surface.

Indirect Source: Any facility, building, structure, or installation, or combination thereof, which generates or attracts mobile source activity that results in emissions of any pollutant (or precursor) for which there is a state ambient air quality standard. Examples of indirect sources include employment sites, shopping centers, sports facilities, housing developments, airports, commercial and industrial development, and parking lots and garages.

Indirect Source Control Program: Rules, regulations, local ordinances and land use controls, and other regulatory strategies of air pollution control districts or local governments used to control or reduce emissions associated with new and existing indirect sources. Indirect source control programs include regulatory strategies such as transportation control measures (e.g., South Coast's Regulation XV for employer-based trip reduction); parking charges; land use controls that reduce the need for vehicle travel and increase transit, bicycle, and pedestrian access; and source-specific regulations such as truck idling and travel schedule requirements.

Indirect Source Review: A major component of an indirect source control program which applies to new and modified indirect sources. Strategies for indirect source review include permit programs, review and comment on new and modified indirect source projects through the California Environmental Quality Act (CEQA) process, and coordination of air quality, transportation and land use policies through local government general plans. Indirect source review reduces emissions from new and modified sources through best available mitigation measures and additional offsite mitigation such as offsets and mitigation fees.

Individual:  An individual is any human being.

Individual Risk:   The increased risk for a person exposed to a specific concentration of a toxicant.

Individual Cancer Risk: The probability, expressed as chances in a million, that a person experiencing 70 years of continuous area-wide outdoor exposure to a toxic air contaminant will develop cancer.

Individual Septic Disposal System (ISDS):  See disposal system.

Indoor Air:   The air that people breathe inside a built environment.

Indoor Air Pollutant: Particles and dust, fibers, mists, bioaerosols, and gases or vapors.

Indoor Air Pollution: Indoor Air Pollution is the term used to describe the amount of contaminants in the air inside a building. Indoor air pollution can often be worse than outside air pollution due to poor ventilation. Unfortunately, it is often ignored. About 80 per cent of all indoor air pollution is human skin. The remaining 20 per cent is usually made up of dust mites, pet dander, smoke, pollen, sweat, and chemical compounds from various substances.

Indoor Air Quality: Indoor Air Quality (IAQ) is a term used to describeThe quality of indoor air relative to its acceptability for healthful human habitation. It is based upon determining the level of pollution of the inside air. The IAQ of any building is measured according to guidelines set by the government and is used as a measuring stick for the efficiency of air purification and filtration systems.

Indoor Climate:   Temperature, humidity, noise, and lighting inside a structure.
Indoor Coil (also Comfort™ Coil or Evaporator Coil): Part of an indoor air unit, it functions with the air conditioner or heat pump outdoors to cool and condition indoor air that flows over it by drawing out heat and moisture.

Indoor/Outdoor System (also Split System):  The combination of an outdoor unit (air conditioner or heat pump) with an indoor unit (furnace or air handler). Split systems must be matched for optimum efficiency.

Indoor Unit:  This is usually located inside the house and contains the indoor coil, fan, motor, and filtering device, sometimes called the air handler.

Induced Draft:  An air flow caused by a fan that draws air through the heat exchanger core in a uniform pattern to dissipate the sensible heat.

Induced Draft Flue System: A term referring to a type of gas heating system equipped with a fan downstream of the furnace. The fan pulls gases from the furnace and propels them to the flue.

Induced Draft Motor:  The draft developed in the heat exchanger of a gas fired furnace by a fan located at the outlet of the heat exchanger, May be used with a natural-draft vent, or with a direct vent system: also called fan-assisted or mechanical draft.

Induced Magnetism:  The ability of a magnetic field to produce magnetism in a metal.

Inducer:  A curved inlet section on an impeller.

Inductance:  A changing current in a coil produces a changing magnetic flux. The changing magnetic flux results in an induced current flowing in the coil. The unit is a Henry.

Induction:  Process by which the primary air sets into motion an air volume, called secondary air, in the room.

Induction Motor:  An ac motor that operates on principle of rotating magnetic field. Rotor has no electrical connection, but receives elec­trical energy by transformer action from field windings.

Inductive Reactance:  The induction of electromagnetic energy in a circuit that creates a counter or reverse voltage as the original current changes.  It may also be thought of as a resistance since it opposes the flow of alternating current. 

Industrial Air Pollution: This term refers to the emissions of the following pollutants: sulfur oxides, nitrogen oxides, mercury, and carbon dioxide. These air emissions contribute to such environmental concerns as urban smog; acid deposition; excessive nutrient loads to important bodies of water, such as the Chesapeake Bay; haze in national parks and wilderness areas; and global climate change.

Industrial Energy Customer: Industrial energy customers include businesses involved in manufacturing or industrial processing.

Industrial Hygienist:  An expert in recognizing and controlling workplace health hazards.

Industrial Source: Any of a large number of sources – such as manufacturing operations, oil and gas refineries, food processing plants, and energy generating facilities – that emit substances into the atmosphere .

Inergen:  Inergen is an environmentally green three dimensional fire suppression agent replacing Halon 1301. Inergen is a blend of three naturally occurring gases – Nitrogen, Argon, and Carbon Dioxide. An Inergen system lowers the oxygen content of the protected area to a point sufficient to sustain human life, but insufficient to support combustion.

Inert:  Chemical inactivity; unable to move; totally un-reactive.

Inert Gas:  One that does not enter into known chemical combination, either with itself or another element. There are four known gases of this type: helium; neon; argon and krypton. Also, a gas that does not supply any of the needs of combustion.

Inert Waste:  Does not contain hazardous waste or soluble pollutants at concentrations in excess of applicable water quality objectives, and does not contain significant quantities of decomposable waste. This type of waste does not need to be discharged at classified waste management units.

Inertia Base:  A concrete foundation with lateral supports which rests upon a number of steel springs. Designed to deal with disturbing frequencies in vibration isolation.
 
Inertia Forces:  When reciprocating compressors run, the moving parts such as pistons, rods, crossheads, connecting rods are repeatedly accelerated and retarded. These velocity changes set up pulsating inertia forces. The forces are of the first and second order. The first order forces have the same frequency as the compressor shaft speed and the second order forces have a frequency twice the shaft speed.

Inertial Bioaerosol Sampler:  Allows the collection of particles by size-selective sampling. See non-inertial bioaerosol sampler.

Inertial Impaction:  Gas filtration: Retention mechanism. Inertial Collection. As the gas stream lines bed in the vicinity of the filter, the carried particles continue in a straight line due to their inertia and impact the filter. Effective primarily for particles about 0.3μm and larger, at high gas velocities and low filter porosity.

Inertial Separators: Air pollution control equipment that uses the principle of inertia to remove particulate matter from a stream of air or gas. See mechanical and cyclone collectors.

Infection:  (1.) The invasion of the body by germs that reproduce and multiply, causing disease by local cell injury, release of poisons, or germ-antibody
reaction in the cells.  (2.) A disease caused by the invasion of the body by germs.

Infectious:  Capable of causing a disease in a susceptible host.

Infiltration: The uncontrolled movement of outdoor air into the interior of a building through cracks around windows and doors or in walls, roofs and floors. This may work by cold air leaking in during the winter, or the reverse in the summer.

Inflammation:   A protective tissue response to injury that destroys, dilutes, or walls off both the injurious agent and the injured tissue, characterized by symptoms such as pain, heat, redness, swelling, and loss of function.

Influent:  The fluid entering a component.

Infrared Lamp:  Electrical device that emits infrared rays; invisible rays just beyond red in the visible spectrum.

Infrared Radiation: Electromagnetic radiation with wavelengths longer than that for light (>700 nanometers). Infrared is often divided into the near infrared (wavelength 800-2000 nm) and the far infrared (>2000nm). Almost all energy radiated by surfaces with a temperature beneath 6000 K is heat radiance. Glass, which is most transparent for visual light radiance (400 nm to 800 nm), is not always transparent to heat radiance. This is the preponderant form of radiation emitted by bodies with moderate temperatures such as the elements of a passive building.

Infrared Thermography: The science of using infrared imaging to detect radiant energy or heat loss characteristics of a building. The infrared camera or scanner electronically senses heat radiated by objects and converts that thermal energy into images visible to the human eye. The camera or scanner, similar to a camcorder in appearance, produces varying shades of black and white images of the building structure. The darker the image, the colder the corresponding surface; the lighter areas are the hotter surfaces. Some scanners can automatically record these images on video, as well as allow the operator to record audio commentary as he/she scans the building. A certain degree of interpretation skill is required to properly assess the images being recorded. Used in conjunction with a blower door, the scanner can provide valuable data, since the pressurization or depressurization can magnify air leakage sites and thermal bypasses.

Infrastructure:  This is the basic supporting structure of an organization. Physical infrastructure in this context refers to the buildings and animal facilities used to house experimental animals.

Ingested Contaminants:  Environmental contaminant that ingresses due to the action of the system or machine.

Ingestion:  Type of exposure that occurs through the mouth.

Inhalable:   Particles small enough to be inhaled, but large enough so that they are not quickly exhaled.

Inhalable Particles: All dust capable of entering the human respiratory tract.

Inhaled Corticosteroid: Anti-inflammatory medication is breathed directly into the lungs. The advantage to this is that the medicine goes directly to where the inflammation is, and has minimal effects on the rest of the body (thus, fewer side effects than corticosteroids taken orally).

Inhaler: See: Metered Dose Inhaler.

Inhalant Allergy:  An Inhalant Allergy is an allergy to something that you can breathe in. Those with allergies to pollen can be described as having an inhalant.

Inhalation:  Type of exposure that occurs through the lungs.

Inhalation Fever:  Flu-like illness following exposure to certain chemical or biological agents (bacteria, fungi, amebae, endotoxin) from an environmental source. Characterized by fever, chills, muscle aches, malaise, and respiratory symptoms. (See Humidifier fever and Pontiac Fever).

Inhibitor:  A chemical that prevents corro­sion or oxidation.Initial Dilution:  The process that results in the rapid and irreversible turbulent mixing of effluent and receiving water around the point of discharge.

Injection Molded ABS:  See “ABS.”  

Injection Well:  Any bored, drilled or driven shaft, dug pit, or hole in the ground into which waste or fluid is discharged, and any associated subsurface appurtenances, and the depth of which is greater than the circumference of the shaft, pit, or hole.

Inlet: An opening providing a means of entrance or intake.

Inlet Covering:  The area of a respirator surrounding the place where air is supplied to the user; it may be a facepiece, helmet, hood, or supplied-air suit; some inlet coverings are tight-fitting and others loose-fitting; see loose-fitting facepiece and tight-fitting facepiece, helmet, hood.

Inlet Diffuser Plenum: Air transition chamber between high-velocity ductwork and an air cleaner. The purpose of the inlet plenum is to slow the incoming airstream down to the collector velocity and provide even air distribution across the face of the air cleaner.

Inlet Pressure:  Is the total pressure (static plus velocity) at the inlet flange of the compressor.

Inlet Temperature:  Is the temperature at the inlet flange of the compressor.

Inlet Throttle:  A compressor control mechanism designed to control performance output of the compressor to the demands of the plant process.

Inlet-Vane Damper: Round multiblade damper mounted to the inlet of a fan to vary the airflow.

Inline Filter:  A filter assembly in which the inlet, outlet and filter element axes are in a straight line.

Innovation & Design Process (ID):  LEED Rating System category. Prerequisites and credits in this category recognize projects for innovative building features and sustainable building knowledge.

Inorganic Compounds:  Compounds that either do not contain carbon or do not contain hydrogen along with carbon, including metals, salts, and various carbon oxides (e.g., carbon monoxide and carbon dioxide).

Inorganic Matter:  Chemical substances of mineral origin, not containing carbon to carbon bonding. Generally structured through ionic bonding.

Input Rating: The measured and assigned rating indicating the level at which an energy-using device consumes electricity or fossil fuel.

INR (Impact Noise Rating): A single figure rating which provides an estimate of the impact sound insulating performance of a floor-ceiling assembly.

Insecticide:  Any material or agent capable of killing insects.

Inside Corner: The point at which two walls form an internal angle, as in the corner of a room.

Inside Drain: In roofing, a drain positioned on a roof at some location other than the perimeter. It drains surface water inside the building through closed pipes to a drainage system.

Inspector:  Any person who performs the duties described as inspecting, sampling and assessing the amount and condition of ACM and Non-ACM materials in a building or other areas that may contain ACM.

Insolation: The amount of solar radiation striking a surface.

Insolubles:  Insoluble material suspended in the lubricating oil. This material may come from contamination or oil degradation.

Inspection:  Critical examination or review.

Inspection and Maintenance Program (I/M program): Auto inspection programs that are required for some polluted areas. These periodic inspections, usually done once a year or once every two years, check whether a car is being maintained to keep pollution down and whether emission control systems are working properly. Vehicles that do not pass inspection must be repaired. Enhanced I/M programs, using special machines to check for such things as how much pollution a car produces during actual driving conditions, are required for some severely polluted areas.

Inspiration: Breathing in.

Instability: The point of operation at which a fan or system will “hunt” or pulse. Common in FC fans and some other fan types where the point of operation is left of the peak of the static-pressure curve.

Instrument:  Used broadly to denote a device that has measuring, recording, indicating, and/or controlling abilities.

Instrument Air:  A quality of compressed air for use with pneumatic instruments and controls. (Usually dry and free from contaminants.)
Insulated Enclosures:  Insulated enclosures are recommended for outdoor applications, to minimize the additional heat load caused be the sun’s rays. It is best to consult your insulation supplier to select the correct material with the right thermal, flame and electrical ratings for your application. In general, a thin layer (about ½ inch) of foam insulation, with the proper flame rating, is sufficient for most applications. (See Non-Metallic Enclosures)

Insulated Glass: Two or more glass panes installed in windows and doors, spaced apart and sealed in a factory.

Insulating Concrete Form (ICF):  Concrete form-wall constructed of foam insulation that remains in place after the concrete cures.

Insulating Glass: Window or door in which two panes of glass are used with a sealed air space between. Also known as Double Glass.

Insulating Glass Unit: Two or more lights of glass spaced apart and hermetically sealed to form a single-glazed unit with an air space between each light. Commonly called IG units.

Insulation: Generally, any material which slows down or retards the flow or transfer of heat. Building insulation types are classified according to form as loose-fill, flexible, rigid, reflective, and foamed-in-place. All types are rated according to their ability to resist heat flow (R-Value). In electrical contracting, rubber, thermoplastic, or asbestos wire covering. The thickness of insulation varies with wire size and type of material, application or other code limitations.

Insulation Board: A rigid structural building board made of coarse wood or cane fiber in 1/2 and 25/32 inch thickness. It can be obtained in various size sheets, in various densities, and with several treatments.

Insulation, Electric:  A substance which has almost no free electrons.

Insulation, Thermal:  A material with low heat conductivity.

Insulation Fasteners: Any of several specialized mechanical fasteners designed to hold insulation down to a steel or a nailable deck.

Insulation Material: A material with a low thermal conductivity (e.g. below 0.2 W/m2K) applied to reduce thermal losses through building envelope (e.g. walls, roofs, floors).

Intact:  Asbestos material that has not crumbled, been pulverized, or otherwise been damaged or disturbed, and the material’s matrix has not noticeably deteriorated.

Intake Filter:  A device for separating solids or suspended particles in the air before they enter the air intake of the compressor.

Intake Filter Silencer:  A device for separating solids or suspended particles in the air before they enter the air intake of the compressor and reduce intake noise as on reciprocating compressors through a silencing chamber in the filter housing.

Intank Check Valve:  A valve designed to prevent air volume and pressure from escaping the compressor tank back into compressor heads while compressor is not operating.

Integrally Controlled Motor (ICM):  A variable-speed motor that operates at low RPM when possible for efficiency and quiet operation. ICM motors are more than 90% efficient versus 60% efficiency for conventional motors.

Integrated Circuit (IC):  A circuit that incorporates multiple transistors and other semiconductors to a single circuit, sometimes called a “chip.”

Integrated Coastal Zone Management:  A continuous and dynamic process by which decisions are made for the sustainable use, development and protection of coastal and marine areas and resources. ICM acknowledges the interrelationships that exist among coastal and ocean uses and the environments they potentially affect.

Integrated Design Team:  The team of all individuals involved in a project from very early in the design process, including the design professionals, the owner's representatives and the general contractor and subcontractors.

Integrated Heating Systems:  HVAC term for a type of heating appliance that performs more than one function, for example space and water heating.

Integrated Pest Management:  A cost-effective way to prevent pests by using less invasive techniques to both animal and occupant alike.

Integrated Sampling Device: An air sampling device that allows estimation of air quality components over a period of time through laboratory analysis of the sampler’s medium. (See also Continuous Sampling Device .)

Integrated Waste Management:  The complementary use of a variety of practices to handle solid waste safely and effectively. Techniques include source reduction, recycling, composting, combustion and landfilling.

Integrity Test:  Used to predict the functional performance of a filter. The valid use of this test requires that it be correlated to standardized bacterial or particle retention test. Examples: Bubble Point Test, Diffusion Test, Forward Flow Test, Pressure Hold Test.

Intelligent Filter Configuration:  This refers to a SEBO upright vacuum cleaner filtration system design that provides less resistance in order to achieve HEPA filtration levels while using less energy.

Intelligent Filter Life Monitor:  This is an IQAir trade name for a filter monitor that takes into account actual use, speed settings and air quality conditions to inform the user when the filter on the air purifiers needs to be replaced. By replacing filters only when truly necessary, the highest air quality is maintained without wasting money by replacing filters before it is required.

IntensiveClean Bags:  This is a Miele trade name for their high filtration dustbags. These bags are an integral part of their certified HEPA filtration system and include a web of three-ply random-spun polymer fibers so that far more tiny particles and allergens are retained than with conventional paper bags. This new dustbag construction has reduced already extremely low dust emissions from Miele dustbags by up to 50%.

Intent:  LEED Green Building Rating System component. Identifies the primary goal of each prerequisite or credit.

Interception:  The process in which a particle is removed from an air stream as it follows the streamlines around a filter. The particle comes in contact with a fiber and stays attached to it because the attractive forces between the fiber and the particle are stronger than the forces of disruption of the moving air stream.

Intercooler:  Heat exchangers for removing the heat of compression between stages of a compressor.

Intercooling:  The removal of heat from the air or gas between stages.

Intercostal:  Situated between the ribs.

Interest: The cost paid to a lender for borrowed money.

Interfacial Tension: Measure of miscibility or solubility of the continuous and discontinuous phases. Increases as miscibility or solubility decreases.

Interim Status:  Legal classification allowing hazardous waste incinerators or other hazardous waste management facilities to operate while EPA considers their permit applications, provided that they were under construction or in operation by November 19, 1980 and can meet other interim status requirements.

Interior Finish: Material used to cover the interior framed areas, or materials of walls and ceilings.

Interior Glazed: Glazing infills set from the interior of the building.

Interlayer: In glazing, any material used to bond two lights of glass and/or plastic together to form a laminate.

Interlocking Shingles: Individual shingles that mechanically fasten to each other to provide wind resistance.
Intermediate Zone:  A zone located between the building’s conditioned space and the outdoors, like a crawl space or attic.

Intermittent Cycle:  A cycle which repeats itself.

Intermittent Ignition:  Ignition system for a gas furnace that operates only when needed or when furnace is operating.

Intermittent Ignition Device: A device that lights the pilot on a gas appliance when the control system calls for heat, thus saving the energy wasted by a standing pilot.

Intermittent Stream:  Carries water runoff only in times of rainfall and remains as a dry channel during other times of the year.

Internal Combustion Engine: An engine in which both the heat energy and the ensuing mechanical energy are produced inside the engine. Includes gas turbines, spark ignition gas, and compression ignition diesel engines.

Internal Dose or Exposure:  That portion of the dose equivalent received from radiation sources inside the human body.

Internal Energy:  Energy which a substance possesses because of the motion and configuration of its atoms, molecules, and subatomic particles.

Internal (heat) Gains: The energy dissipated inside the heated space by people (body heat) and appliances (lighting, cooker, etc.). A proportion of this energy contributes to the space heating requirements (kWh).

Internal Heat Load:  The heat generated by the components inside the cabinet.

Internal Leakage:  On vacuum cleaners and air purifiers, filtration is only effective on the air that passes through the filter system. Internal leakage refers to air that escapes the unit before it is filtered. This is an important consideration because such air often takes particles and contaminants that were on surfaces and makes them airborne, where they may stay suspended for hours and are more easily inhaled. If an appliance leaks air before the filters then its filtration claims are only theoretical. That's why some companies such as Miele and IQAir, certify the HEPA filtration of the entire vacuum cleaner or air purifier to demonstrate that there is no internal leakage.

Internal Ribs:  This is a vacuum cleaner design used by Miele and other companies that employs integrated plastic ribs as part of the dustbag compartment. This design helps prevent airflow loss as the bag fills and increases the longevity of the bags by circulating air around the entire bag, not just the rear.

Internal Sources: The sources of internal heat such as appliances, lights and people . See internal heat.

Internally Wired Wand:  Like electric hoses, an internally wired wand is one where the electrical cord runs inside rather than on the outside of the wand. Such wands may have pigtails an either or both ends or may be of the Direct Connect type.

International Agency for Cancer (IARC): An expert international agency of the World Health Organization which publishes evaluations of evidence on the carcinogenicity of a wide range of chemicals.

International Air Pollution: Pollution that moves across national borders. The 1990 Clean Air Act includes provisions for cooperative efforts to reduce pollution that originates in one North American country and affects another.

International Commission on Radiological Protection (ICRP):  International organization that studies radiation, including its measurement and effects.

International Organization for Standardization:  ISO.

Interply: Between two layers of roofing felts that have been laminated together.

Interquartile Range (IQR):  Distance between the top of the lower quartile and the bottom of the upper quartile, which provides a measure of the spread of data.

Interstate Air Pollution: Pollution that moves across state borders. Because often, air pollution moves out of the state in which it is produced into another state, the 1990 Clean Air Act includes many provisions, such as interstate compacts, to help states work together to protect the air they share.

Interstate Commerce Commission:  Government body which controls the design and construction of pressure containers.

Interstate Waters:  All rivers, lakes, artificial impoundments, and other waters that flow across or form a part of the boundary with other states or Mexico.

Interstices:  Spaces or openings in a filtration medium. Also referred to as pores or voids.

Interstital:  Pertaining to the openings in a filtration medium.

Interrupted Cycle:  A cycle that does not repeats it self.

Interstices: The openings between the interlacings of the warp and filling yarns, such as the voids.

Intraperitoneal:  Within the peritoneal cavity. An intraperitoneal injection is made into the peritoneal cavity in the abdomen.

Intravenous:  Within a vein. An intravenous injection is made into a vein.

Intrinsic Asthma: When asthma symptoms are not caused by exposure to allergens.

Intrinsic Heat: Heat from human bodies, electric light bulbs, cooking stoves, and other objects not intended specifically for space heating.

Intrinsically Safe:  Where any spark or thermal effect that may occur in normal use, or under any conditions of fault likely to occur in practice, is incapable of causing an ignition of the prescribed flammable gas, vapor or dust.

Intrinsically Safe Respirator:  A respirator that has been certified as not being a source of ignition.

Intubation: The process of putting a tube down someone’s throat into the trachea; the tube is connected to a respirator or ventilator that pushes measured amounts of air into the lungs (and then lets it out again) to help the person breathe. This can save the life of a person having a severe asthma episode, but it also has many risks and possible complications.

Inventory Analysis:  The first stage of life cycle assessment, in which the inputs and outputs of materials and energy are determined for a process, product, or facility.

Inversion: A layer of warm air in the atmosphere that prevents the rise of cooling air and traps pollutants beneath it.

Invertebrate:  An animal without a back-bone or spinal column.

Inverter Control:  A type of electronic control used with DC motors.

Ion:  An electrically charged atom or group of atoms that has lost or gained electrons; a loss makes the resulting particle positively charged; a gain makes the particle negatively charged.

Ion Exchange Columns:  Vessels filled with ion exchange resin (anion, cation, or mixed) for producing conditioned or DI Water. Also, type of column used for Ion Exchange Chromatography.

Ionic Air Purifiers:  Ionic Air Purifiers are relatively new technology. When operating, the ionic air purifier produces a “spray” of invisible negative ions from a small needle-like point usually located on the top. These negatively charged ions release into the room’s air and naturally circulate. Your ionic unit produces a steady stream of negatively charged ions, which then attach themselves to surrounding positively charged airborne particles.

Ionic Silver Stick:  This is an Air-O-Swiss trade name for a device that protects water in its humidifiers from microorganisms. It uses a technology that automatically disperses silver ions at the correct concentration to keep water germ, bacteria, fungi and virus free.

Ionizer:  A device that removes airborne particles from breathable air. Negative ions are produced and give up their negative charge to the particles. These new negative particles are then attracted to the positive particles surrounding them. This accumulation process continues until the particles become heavy enough to fall to the ground.

Ionizing:  Turning an atom into an ion by giving the atom a positive or negative electrical charge.

Ionizing Radiation:  Any radiation (alpha, beta, or gamma) that directly or indirectly displaces electrons from the outer domains of atoms.

IPLC:  Integrated Port Load Capacity is the cooling capacity of the system operating at part load conditions.

IPLV:  Integrated Port Load Value is the efficiency performance factor at part load cooling capacity. This performance is critical due to the higher quantity of operating hours under part load conditions than at full load.

IPM: Integrated pest management.

IPS (Iron Pipe Size): Pipe thread sizing system. Also measurement of the outside diameter of a pipe.

IR Drop:  A voltage drop, IR meaning Current times resistance and equaling voltage (Ohm’s Law).

IRMA [Insulated (or Inverted) Roof Membrane Assembly]: In this system the roof membrane is laid directly on the roof deck, covered with extruded foam insulation and ballasted with stone, minimum of 1000 lbs. per square.

Irradiance (at a point of a surface): Quotient of the radiant flux dX, incident on an element of the surface containing the point, by the area dA of that element. Equivalent definition: Integral, taken over the hemisphere visible from the given point, of the expression Le cos Y.dX. where Le is the radiance at the given point in the various directions of the incident elementary beams of solid angle dX where Y is the angle between any of these beams and the normal to the surface at the given point.

Irradiated Food:  There are several types of radiant energy used to sterilize foods. Gamma irradiation is commonly used to sterilize laboratory animal
feeds. The amount of irradiating energy is controlled to kill all microorganisms, without affecting the quality of the food.

Irradiation: See radiation.

Irreversible Disassembly:  Disassembly in which brute force is used to recover the bulk of the principal materials from a product, and in which no refurbishment and reuse of components or modules is possible.

Irreversible Process:  One in which a portion of the original system energy is dissipated and cannot be returned to the system through its own operation. The system and/or
surroundings cannot be returned to their original state.

Irrigation: Lawn sprinkler system.

Irritant: A substance that causes irritation of the skin, eyes, or respiratory system. Effects may be acute from a single high-level exposure, or chronic from repeated low-level exposures to such compounds as chlorine, nitrogen dioxide, and nitric acid.

Isentrop:  A process taking place without any heat exchange with the surroundings.

Isentropic: An adjective describing a reversible adiabatic process a change taking place at constant entropy.

Isentropic Compression:  An adiabatic compression with no increase in entropy; a reversible-adiabatic compression.

Isentropic Efficiency:  The ratio of the real gas isentropic power consumption to shaft input.

Isentropic Power Consumption:  The power which is theoretically required to compress a gas under constant entropy from a given inlet pressure to a given discharge pressure. (Calculated assuming ideal conditions.)

ISO: The International Standards Organisation, based in Geneva.

ISO 9000:  A family of international standards for quality management and assurance.

Iso-: The (l) prefix meaning constant: as in isothermal (constant temperature); isentropic (constant entropy); isobaric (constant pressure); etc.; and (2) in chemicals, one having different characteristics but with the same number and kind of atoms.

ISO Cleanroom Classifications:  Adoption of ISO standards makes national standards such as AS 1386 redundant. Air cleanliness classifications are in ISO-14644-1 Classification by Airborne Particles. This is complemented by ISO-14698, dealing with bio-contamination control and monitoring.

Isobar:  A process taking place under constant pressure. To change the volume from state 1 to state 2, heat must be removed. The temperature change is proportional to the change in specific volume.

Isobaric: An adjective used to indicate a change taking place at constant temperature.

Isobutane:  A flammable hydrocarbon refrigerant.

Isochor:  A process taking place under constant volume. To raise the pressure from state 1 to state 2, heat must be added. The pressure change is proportional to the change in temperature.

Isocyanates:  Reactive and toxic compounds used in the plastics industry, and found in urethane, polyurethane, and paint hardeners.

Isolation Barriers:  Installed temporary hardwall barriers that complete the containment enclosure and establish the regulated abatement work area.

Isolation Valves:  Valves used for the transfer and isolation of refrigerant charge in the cooler or condenser, allowing refrigerant to be stored inside a chiller during servicing.

Isotherm:  Is a process taking place under constant temperature. To compress the gas from state 1 to state 2, heat must be removed to keep the temperature constant. The pressure change is reciprocal to the change in specific volume.

Isothermal:  Changes of volume or pressure under conditions of cons­tant temperature.

Isothermal Compression:  Is a compression in which the temperature of a gas remains constant.

Isothermal Efficiency:  The ratio of the isothermal power consumption to shaft input.

Isothermal Power Consumption:  The power which is theoretically required to compress a gas under constant temperature, in a compressor free from losses, from a given inlet pressure to a given discharge pressure.

Isoconcentration: More than one sample point exhibiting the same isolated concentration.

Isolated Gain: The transfer of heat into the space to be heated from a collector that is thermally isolated from the space to be heated by physical separation or insulation (such as an attached sunspace with an insulated common wall).

Isothermal: An adjective used to indicate a change taking place at constant temperature.

Isotopes:  Forms of an element having the same number of protons in their nuclei, but differing numbers of neutrons.

Isotropic (Symmetric) Membrane:  Membrane in which the pore openings are the same diameter throughout the thickness and on both sides of the membrane. Non-directional, their flow characteristics are independent of which side faces the feed stream.