NACE: National Association of Corrosion Engineers.

NACHI Foundation: A Maryland based charitable organization funded by members of the National Association of Certified Home Inspectors.

NAFA:  National Air Filtration Association.

Nailer: A piece of lumber secured to non-nailable decks and walls by bolts or other means, which provides a suitable backing onto which roof components may be mechanically fastened.

Nanometer: Unit of wavelength equal to 10-9 meter.

Nano-meters (nm): Unit used to measure short wavelengths in electromagnetic radiation 1 nm = 10-9m. See also infra-red radiation, visible radiation.

Napped: The rupturing of the filling yarns to produce a fleecy surface on woven fabrics.

Nasal Cannula: A light-weight tube with two hollow prongs that fit just inside the nose. Nasal cannulas are used to deliver oxygen.

Nasal Spray: Medication used to prevent nasal allergy symptoms. Available by prescription or over-the-counter in decongestant, corticosteroid or salt-water solution form.

NASCSP: National Association for State Community Services Programs.  NASCSP's mission is to assist state in responding to poverty issues. NASCSP members are state administrators of the Community Services Block Grant (CSBG) and U.S. Department of Energy's Weatherization Assistance Program (DOE/WAP). The CSBG, administered by the states, provides core funding to local agencies to reduce poverty, revitalize low-income communities and to empower low-income families to become self-sufficient. The DOE/WAP helps low-income families reduce their energy costs by making homes more energy efficient. The local agencies funded by these programs provide a wide range of services such as weatherization, energy assistance, child care, job training, and housing. NASCSP keeps its members, the federal government, and other interested parties informed about issues related to CSBG and DOE/WAP through its publications.

NATA:  NATA is Australia’s national provider of laboratory and inspection accreditation services and GLP compliance monitoring.

NATE:  North American Technician Excellence — certification acknowledging a dealer/technician as the one of the most knowledgeable and experienced at installing and servicing high performance, precision-engineered heating and cooling systems.

National Ambient Air Quality Standards (NAAQS): Standards established by the United States EPA that apply for outdoor air throughout the country. There are two types of NAAQS. Primary standards set limits to protect public health and secondary standards set limits to protect public welfare.

National Emissions Standards for Hazardous Air Pollutants (NESHAPS): Emissions standards set by EPA for an air pollutant not covered by NAAQS that may cause an increase in fatalities or in serious, irreversible, or incapacitating illness. Primary standards are designed to protect human health, secondary standards to protect public welfare (e.g. building facades, visibility, crops, and domestic animals).

National Environmental Policy Act (NEPA):  Federal legislation enacted in 1969 that requires all federal agencies to document and consider environmental impacts for federally funded or approved projects and the legislation under which DOE is responsible for NEPA compliance at LLNL.

National Institute for Standards and Technology (NIST):  Federal agency, formerly known as the National Bureau of Standards, responsible for reference materials against which laboratory materials are calibrated.

National Low Emissions Vehicle Program (NLEV):  A program that creates voluntary requirements that U.S. automakers can adopt in lieu of compliance with other vehicle emission control measures. The program applies to the manufacture of new light-duty vehicles and new light-duty trucks up to 6,000 lb gross vehicle weight rating (GVWR).

National Pollutant Discharge Elimination System (NPDES) Permit:  Permit required for all point sources discharges of pollutants to surface waters. It has the following characteristics: issued for up to five years; provides for inspection and monitoring; requires notice to the public, the USEPA and any other affected state, provides for the protection of navigation, and mandates a pre-treatment program as necessary.

National Pollutant Release Inventory (NPRI): A Canadian program, created in 1992, to provide information on pollutants released to the environment and transferred for disposal. Reporting of NPRI is mandated under the Canadian Environmental Protection Act (CEPA) and is due by June 1 of the following year. Each year, Environment Canada updates the NPRI substance list and revises reporting criteria after consultation with stakeholders.

Natural Citing Criteria:  An approach where the locations of roads, buildings, and other structures are selected to be where the geological and biological factors are most favorable; essentially “working with nature” when selecting locations for human-made structures.

Natural Convection: Heat transfer between a surface and adjacent fluid (usually air) and by the flow of fluid from one place to another, induced by temperature differences rather than by mechanical means, also called free convection. Compare with forced convection.

Natural Convection Air Cooler: An air cooler depending on natural convection for air circulation.

Natural-Draft Furnace:  A furnace in which the natural flow of air from around the furnace provides the air to support combustion. It also depends on the pressure created by the heat in the flue gases to force them out through the vent system.

Natural Finish: A transparent finish which does not seriously alter the original color or grain of the natural wood. Natural finishes are usually provided by sealers, oils, varnishes, water-repellent preservatives, and other similar materials.

Natural Frequency:  A projecting aperture at the end of a tube, pipe etc. serving as an outlet for compressed air. Reduces the demand on the compressor by generating the highest thrust and volume for the lowest possible air consumption.

Natural Gas: A naturally occurring mixture of hydrocarbon and nonhydrocarbon gases found in porous geological formations beneath the earth's surface, often in association with petroleum. The principal constituent is methane. Underground deposits of gases consisting of 50 to 90 percent methane (CH4) and small amounts of heavier gaseous hydrocarbon compounds such as propane (C3H8) and butane (C4H10).

Natural Light: Visible part of direct solar radiation. (Note: when dealing with actinic effects of optical radiations, this term is commonly used for radiations extending beyond the visible region of the spectrum.)

Natural Lighting System: Component or a series of components joined in a specific building for natural daylighting.

Natural Receiving Water Temperature:  The temperature of the receiving water at locations, depths, and times which represent conditions unaffected by any elevated temperature waste discharge or irrigation return waters.

Natural Sources: Non-manmade emission sources, including biological and geological sources, wildfires, and windblown dust.

Natural Ventilation: Ventilation using only natural air movement without fans or other mechanical devices. Air which enters a building controlled, through open windows or other openings, due to wind pressure or temperature differences between the outdoor and indoor air.
 
Navigable Water:  Any surface body of water.

N.B.:  ACRONYM – National Board of Boiler and Pressure Vessel Inspectors.

NBC:  Nuclear, Biological, Chemical.

NBCD:  Nuclear, Biological and Chemical Defense.

N.C.:  Normally closed contacts of a relay. Contacts are close-circuited when the relay is de-energized.

Ncm:  Non-Commissioned Members.

N cu m/min N cu m/hr:  Volume flow rate measured in normal cubic metres per minute (or hour), i.e. related back to normal inlet conditions.

NDHQ:  National Defense Headquarters.

NEAT (National Energy Audit): Created by Oak Ridge National Laboratories as a DOE approved audit qualifying for the 40% materials waiver. It is a computerized auditing tool for prioritizing energy conservation measures for houses.

Neat Plaster: A base coat plaster which does not contain aggregates and is used where the addition of aggregates on the job is desired.

NEC:  Acronym for National Energy Council or National Electric Code used in North America. A set of rules governing safe wiring methods. Local codes – which are backed by law – may differ from the NEC in some ways.

NEDS: National Emission Data System.

Needed Felt: A felt made by the placement of loose fiber in systematic alignment with barbed needles. The needles move up and down, pushing and pulling fibers to form an interlocking of adjacent fibers. It is the most commonly used construction method since it is stronger than pressed felt.

Needle Valve:  A valve having a slender point fitting into a conical seat, used to regulate accurately the flow of a liquid or gas.
                                                                                                                  
NEMA:  Acronym for the National Electrical Manufacturing Association – Your equipment may require a NEMA rating to comply with local codes. See page 9 for chart of NEMA Enclosure Ratings. Air conditioners typically carry an agency marking such as UL (Underwriters Laboratories), which designates the environmental hazard from which the contents are being protected. This marking should be matched to the enclosure to be cooled. Typical examples include NEMA 12, (indoor use, protection from dust and dripping liquids), NEMA 3R, (outdoor use and rain proof) and NEMA 4/X (outdoor or indoor use, protection from wash-down and corrosive environments). Depending upon the NEMA enclosure type, an air conditioner can be provided to operate in most locations. Locations subject to dust, dripping liquids, rain, washdown and corrosive atmospheres can utilize these “Special Purpose Air Conditioners.”

NESHAP:  National Emission Standards for Hazardous Air Pollutants (40 CFR Part 61).

Nebulizer: A machine that turns liquid medication into a mist for inhaling.

Needle Gauge:  A measuring tool used to check air pressure at the tool by inserting a hypodermic needle into the rubber hose.

Needle Scaler:  A hand held pneumatic chipping tool which the blows are transmitted through a group of floating needles or metal rods.

Needlefelt:  A nonwoven fabric where staple fibers are entangled together through a manufacturing process using barbed needles, providing for a heavy weight filter fabric, which can filter air-borne particles for use in baghouses and suspended particles in liquids from lighter weight needlefelt fabrics for use liquid bag filtration.

Needlepoint Ionizers: Needle ionizers use high voltage electricity to create negative electrons. These electrons run up the length of a pointed spike, or needle, where they stream into the air and attract oxygen molecules. At this point, they become negative ions and are attracted to airborne particles. These molecules build up around the particles until they become too heavy to remain air borne and float to the ground. This process is known as agglomeration.

Negative Air Pressure Equipment:  A local exhaust system, capable of maintaining air pressure within a containment at a lower pressure than the air pressure outside of such containment, and which provides for HEPA filtration of all air exhausted from the containment.

Negative Declaration:  A California Environmental Quality Act document issued by the lead regulatory agency when the initial environmental study reveals no substantial evidence the proposed project will have a significant adverse effect on the environment, or when any significant effects would be avoided or mitigated by revisions agreed to by the applicant.

Negative Ion: Negative ions are odorless, tasteless, and invisible molecules that we inhale in abundance in certain environments. Think mountains, waterfalls, and beaches. Once they reach our bloodstream, negative ions are believed to produce biochemical reactions that increase levels of the mood chemical serotonin, helping to alleviate depression, relieve stress, and boost our daytime energy.

Negative Ion Generator:  An ion generator that can be used for air cleaning purposes by applying static charges to remove particles from indoor air.

Negative Ionizing Filter: A Negative Ionizing Filter is a device which electrically charges the air inside it and uses a fan to blow it out into the room. This charged air causes particles in it to become attracted to the walls and furniture in the room. This can lead to a process known as the Black Wall Effect.

Negative Pressure: A pressure below atmospheric. In residential construction negative pressure often refers to pressures around the house that is less than the indoor or the pressures on e.g. the windward side of the house: such variations in pressure will encourage infiltration by cross ventilation.

Negative Pressure Respirator (tight fitting):   A respirator in which the air pressure inside the facepiece is negative during inhalation with respect to the ambient air pressure outside the respirator.

Negative Pressure Seal Check:  A verification by the user that a respirator is properly seated to the face; it involves blocking the air inlet and reducing pressure inside the facepiece by inhalation.

NEMA:  National Electrical Manufacturing Association.

Neoprene: A synthetic rubber having physical properties closely resembling those of natural rubber. It is made by polymerizing chloroprenes, which are produced from acetylene and hydrogen chloride.

Nephrotoxin:  A chemical which has a primary toxic effect on the kidneys.

NEUROTOXIN: A chemical which has a primary toxic effect on the central nervous system. Styrene, mercury, carbon disulfide.

NESHAP: National Emissions Standards for Hazardous Air Pollutants.

Nesting: A method of re-roofing with new asphalt shingles over old shingles in which the top edge of the new shingles is butted against the bottom edge of the existing shingle tab.

Net Free Area: The area of a vent after that area has been adjusted for insect screen, louvers, and weather covering. The free area is always less than the actual area.

Net Generation: Gross generation minus plant use from all electric utility owned plants. The energy required for pumping at a pumped storage plant is regarded as plant use and must be deducted from the gross generation.

Net Load Coefficient (NLC): Net reference load per degree of indoor-minus-outdoor temperature difference per day

Net Present Value:  Determination of current value of buildings and components in today’s dollars that reflects a stream of current and future benefits and costs; projected future costs and benefits must be discounted to give a fair value in today's dollars.

Net Reference Load: Steady-state heat loss from a building, excluding the solar wall, assuming constant indoor temperature. Compare with net load coefficient (J).

Neuroleptanalgesia:  Neuroleptanalgesia is defined as a state of quiescence, altered awareness, and analgesia produced by the administration of a combination of a neuroleptic agent and a narcotic (opioid) analgesic.

Neurological: Relating to the nervous system ― the entire integrated system of nerve tissue in the body, brain, brainstem and spinal cord.

Neurological Disorders: Disorders of the central nervous system (brain, brainstem and cerebellum), the peripheral nervous system (including cranial nerves), and the autonomic nervous system (parts of which are located in both central and peripheral nervous system). Major conditions include: headache; dementia, including Alzheimer’s disease; seizures and epilepsy; sleep disorders; infections; movement disorders such as Parkinson’s disease; and spinal cord disorders.

Neuroma:  A neuroma is a tumor growth of nerve cells and fibres. It may occur at the end of an injured nerve fibre.

Neurotoxin:  A substance that can cause damage to nerve cells or the nervous system.

Neutral Temperature: See Comfort temperature.

Neutral Wire: Usually color-coded white, the neutral wire carries electricity from an outlet back to the service panel. Also see Hot Wire and Ground.

Neutralizer:  A substance used to counter act acids.

New Discharge:  Any discharge (a) that is not presently taking place unless waste discharge requirements have been established and construction has commenced, or (b) which is presently taking place and for which a material change is proposed but no construction has commenced.

New Source: A stationary source; the construction or reconstruction of which is commenced after the proposal date of the standard. Also NSPS (New
Source Performance Standard).

New Source Performance Standards (NSPS):  U.S. federal standards promulgated for major and minor sources on a category-category basis. NSPS are national emission standards that are progressively tightened over time to achieve a steady rate of air quality improvement without unreasonable economic disruption. The NSPS imposes uniform requirements on new and modified sources through the nation. These standards are based on the best demonstrated technology (BDT).

New Source Review (NSR):  A program used in development of permits for new or modified industrial facilities which are in a non-attainment area, and which emit criteria air pollutants. The two major requirements of NSR are Best Available Control Technology (BACT) and emission offset.

NEWTRIT:  Model used to calculate doses from environmental measurements.

New York State Green Building Tax Credit: A tax incentive program introduced by Governor George e. Pataki providing tax credits to encourage green building.

Newel: A post to which the end of a stair railing or balustrade is fastened. Also, any post to which a railing or balustrade is fastened.

NFPA:  ACRONYM – National Fluid Power Association.

NFPA Hazard Rating:  Classification of a chemical by a four-color diamond representing health, flammability, reactivity and specific hazard by a numbered hazard rating from 0 – 4.

NFR:  Non-fiber releasing. A filter which will not release fibers into the filtrate.

NFSI:  National Floor Safety Institute (www.nfsi.org), a non-profit organization with a mission to aid in the prevention of slip-and-fall accidents through education, training and research. Conducts laboratory and field testing to determine walkway materials, floor maintenance products and coatings that have achieved safety benefits worthy of NFSI certification.

Niche:  An organisms “occupation,” or how it lives.

Night Insulation: Movable insulation that covers a glazing at night and is removed during the day.

Night Radiance: Heat radiance which appears at night. When the sky is clear at night a surface facing the sky sends and receives heat radiance to and from the sky. The radiant temperature of a clear sky is usually well below zero, particularly at night. Because of this the surface temperature can easily descend below the ambient outdoor air temperature.

Night Ventilation: Ventilation which takes place outside the normal operating time of the building.

NIH: National Institute of Health.

NIOSH:   National Institute for Occupational Safety and Health.

Nipple: A short pipe installed between fittings. A pipe coupling that is threaded on both ends.

Nitrate (NO3):  A class of chemical compounds having the form NO3.  Typically formed when ammonia is degraded by microorganisms in soil or groundwater.

Nitric Oxide (NO): Precursor of ozone, NO2, and nitrate; nitric oxide is usually emitted from combustion processes. Nitric oxide is converted to nitrogen dioxide (NO2) in the atmosphere, and then becomes involved in the photochemical processes and / or particulate formation. (See Nitrogen Oxides.)

Nitrile Rubber:  Nitrile rubber is a copolymer of acrylonitrile and butadiene.  Nitrile rubber offers excellent physical hazard resistance to punctures, cuts, snags and abrasion.  Nitrile rubber has considerable resistance to oils, fuels, and certain organic solvents.  It is not flame resistant.

Nitrite (NO2):  An intermediate product in many nitrogen transformations.

Nitrogen (N2):  A gas that comprises 78% of the earth’s atmosphere by volume. An essential plant nutrient.

Nitrogen Dioxide:  (One of the NOx); smog forming chemical.

• Source:  Burning of gasoline, natural gas, coal, oil, etc.  Cars are an important source of NO2.
• Health Effects:  Lung damage, illnesses of breathing passages and lungs (respiratory system).
• Environmental Effects:  Nitrogen dioxide is an ingredient of acid rain (acid aerosols), which can damage trees and lakes.  Acid aerosols can reduce visibility.
• Property Damage:  Acid aerosols can eat away stone used on buildings, statues, monuments, etc.

Nitrogen Oxides (NOx): A colorless, poisonous gas. It is a by-product of gas combustion.  Gases composed of nitrogen and oxygen that can transform into acidic air pollutants. NOx are released into the air through the use of chemical fertilizers for agriculture and the combustion of fuel. They play a major role in the formation of smog.

NJC:  National Joint Council.

NL:  ACRONYM – Non-lubricated compressor.

NM: A type of Romex cable (nonmetallic sheathed cable that contains several conductors). The cable, which is flame-retardant, is limited to use in dry locations only and can not be exposed to excessive moisture.

NMC (Non Metallic Conduit): A type of Romex cable (nonmetallic sheathed cable that contains several conductors). NMC may be used in damp or corrosive locations as well as dry areas.

NMDA Receptors:  N-methyl-D-aspartate (NMDA) receptors are important for the transmission of some aspects of pain in the central nervous system. In particular, they appear to be involved in the development of hypersensitivity that accompagnies injuries or inflammation.

NM³/HR:  Unit of free air flow rate. Normal cubic meter per hour. The air in the following conditions: 1.013 bar(a) of pressure; 0 degrees Celsius of temperature and 0% of relative humidity.

N.O.:  Normally open contacts of a relay. Contacts are open-circuited when relay is de-energized.

NO2:   Nitrogen Dioxide.

Noise Criteria Curves (NC Curves):  Curves that define the limits which the octave band spectrum of a noise source must not exceed if a certain level of occupant acceptance is to be achieved.

Noise Reduction (NR): The difference between the average sound pressure levels of two spaces. Usually these two spaces are two adjacent rooms called, respectively, the source room and the receiving room.

No Load:  The air compressor continues to run, usually at full RPM, but no air is delivered because the inlet is either closed off or modified, not allowing inlet air to be trapped.

No Observable Adverse Effect Level (NOAEL):  An exposure level at which there are no statistically or biologically significant increases in the frequency or severity of adverse effects between the exposed population and its appropriate control; some effects may be produced at this level, but they are not considered as adverse, or as precursors to adverse effects. In an experiment with several NOAELs, the regulatory focus is primarily on the highest one, leading to the common usage of the term NOAEL as the highest exposure without adverse effects.

No-Cutout Shingles: Shingles consisting of a single, solid tab with no cutouts.

No-Observed-Adverse-Effect-Level (NOAEL): A term used in risk assessment. An exposure level at which there are no statistically or biologically significant increases in the frequency or severity of adverse effects between an exposed population and a comparable non-exposed population.

No-Observed-Effect-Level (NOEL): A term used in risk assessment. An exposure level at which there are no statistically or biologically significant difference or severity of ant effect between an exposed population and a comparable non-exposed
population.

Noise Criteria: A way for an architect to specify the maximum permissible sound power level in each of the eight octave bands NC curves give. In a graphical form, maximum permissible intensity per octave band.

Noise Reduction Rating (NRR):  The difference between the overall C-weighted sound level of a noise spectrum having equal energy per octave and the resulting A-weighted noise levels under a hearing protection device.

Nomimal: An arbitrary term used to describe the degree of filtration and generally not comparable or interchangeable between products or manufacturers. A user should always ask for a copy the test procedure used and results from the manufacturer’s lab notebook to understand each rating.

Nominal Efficiency:  An arbitrary filter efficiency rating.

Nominal Filter Rating:  Filter rating indicating the approximate particle size for which the majority will not pass through a given filter. It is generally interpreted as meaning that 85% of the particles of size equal to the nominal filter rating will be retained by the filter.

Nominal Micron Rating:  A term that means that 98% of all particles larger than a stated micron size have been removed from the product being filtered through the filter element.

Nominal Size: Size used for identification only; not literal dimensions.

Nonattainment Area: A geographic area identified by the U.S. EPA and / or CARB as not meeting either NAAQS or CAAQS standards for a given pollutant.

Nonattainment Transitional: A subcategory of the nonattainment designation category for state standards that signals progress and implies the area is nearing attainment. Districts with nonattainment-transitional status may revise their attainment plans to delay adoption of control measures anticipating attainment without the measures.

Noncarcinogenic Effects: Non-cancer health effects which may include birth defects, organ damage, morbidity, and death.

Noncombustible Materials:  Materials that under ordinary conditions will not burn. Composite materials are determined to be noncombustible if they successfully pass the test criteria contained in ASTM E-136, Test for Behavior of Materials in a Vertical Tube Furnace at 750 Degrees C.

Noncondensables:  Are those constituents in the suction gas that cannot be condensed to a liquid with the cooling medium available.

Nonconductors (Insulators):  Nonconductors resist electron flow. The atoms have almost no free electrons. Examples would be: A perfect vacuum, quartz, glass, ceramics, rubber, wood, plastics.

Noncooled Compressor Cylinders:  Reciprocating type compressor used mainly in oil and gas field applications. The compressor cylinders operate at low compression ratios and experience small temperature rise.

Noncorrosive Gas:  Is one that does not attack normal materials of construction.

Nonfibered Roof and Foundation Coating: Dual purposed, this thin-viscosity material doubles as a nonfibered roof or foundation coating.

Nonflammable Medical Gas: A compressed gas, such as oxygen or nitrous oxide, which is nonflammable and used for therapeutic purposes.

Nonhazardous Waste:  Waste that is not classified as hazardous.

Nonlubricated Compressor:  A compressor designed to compress air or gas without contaminating the flow with lubricating oil. Piston rings and packing are usually made of TFE-based materials or carbon or other synthetic material that operate without lubrication.

Nonpolar:  Compound or element that’s electron capacity is satisfied. A neutral condition that will remain un-reactive. Not polar. See Polar.

Nonwoven:  A filter fabric that is formed of natural or synthetic fibers that are randomly oriented in filtration media. Typically, held together with a binder or fibers are entangled.

Non-Asbestos Material:  Any material documented to contain one percent (1%) or less of asbestos.

Non-attainment Area:  A geographic area in which the level of a criteria air pollutant is higher than the level allowed by the federal standards. A single geographic area may have acceptable levels of one criteria air pollutant but unacceptable levels of one or more other criteria air pollutants; thus, an area can be both attainment and non-attainment at the same time. It has been estimated that 60% of Americans live in non-attainment areas.

Non-Bearing Wall: A wall supporting no load other than its own weight.

Non-Destructive: A phrase describing a method of examining the interior of a component whereby no damage is done to the component itself.

Non-Drying (Non-Curing): A sealant that does not set up or cure. See Butyl.

Non-hazardous Solid Waste:  All putrescible (able to rot quickly enough to cause odors and attract flies) and nonputrescible solid, semi-solid and liquid wastes, including garbage, trash, refuse, paper, rubbish, ashes, industrial wastes, demolition and construction wastes, abandoned vehicles and parts thereof, discarded home and industrial appliances, manure, vegetable or animal solid and semi-solid wastes and other discarded solid or semisolid waste; provided that such wastes do not contain wastes which must be managed as hazardous wastes, or wastes which contain soluble pollutants in concentrations which exceed applicable water quality objectives, or could cause degradation of waters of the state (i.e.: designated waste).

Non-fibered Aluminum Roof Coating: Thin but efficient reflective barrier to reflect sun's harmful rays and prolong surface life. Also works on metal surfaces.

Non-Friable:  Any material that when dry, can not be crumbled, pulverized, or reduced to powder by hand pressure, and is not capable of being released into the air by hand pressure.

Non-Friable Organically Bound (NOB) Asbestos Material: Non-friable asbestos materials embedded in flexible-to-rigid asphalt or vinyl matrices, including but not limited to flooring materials, adhesives, mastics, asphalt shingles, roofing materials and caulks. 

Non-Industrial Source: Any of a large number of sources – such as mobile, area-wide, indirect, and natural sources – which emit substances into the atmosphere.

Non-Metalic Enclosures:  Although plastics have better insulating properties than metal, a layer of insulation is still recommended for outdoor applications. (See Insulated Enclosures)

Non-Methane Hydrocarbon (NMHC):  The sum of all hydrocarbon air pollutants, excluding methane; significant precursors to ozone formation.

Non-Methane Organic Gases (NMOG): The sum of all organic air pollutants, excluding methane. NMOG account for aldehydes, ketones, alcohols, and other pollutants that are not hydrocarbons but are precursors of ozone.

Non-Point Source: Diffuse pollution source (i.e. without a single point of origin or not introduced into a receiving stream from a specific outlet). The pollutants are generally carried off the land by storm water. Common nonpoint sources are agriculture, forestry, urban, mining, construction, dams, channels, land disposal, saltwater intrusion, and city streets. May be referred to as area source.

Non-Potable Water:  Undrinkable water.

Non-Road Emissions: Pollutants emitted by combustion engines on farm and construction equipment, gasoline-powered lawn and garden equipment, powerboats, outboard motors, and some portable equipment.

Non-Sag: A sealant formulation having a consistency that will permit application in vertical joints without appreciable sagging or slumping. This performance characteristic allows the sealant to be installed in a sloped or vertical joint application without appreciable sagging or slumping.

Non-Skinning: Descriptive of a product that does not form a surface skin.

Non-Staining: Characteristic of a compound that will not stain a surface.