M

m3

cubic meter

MAAC

maximum ambient air concentration

MAER

maximum allowable emission rate

mf

molecular formula

MF

modifying factor

MFBI

major fuel burning installation

MFC

metal finishing category

MFM

mass flowmeter

mg

milligram (1/1000th of a gram)

mg/kg

milligrams per kilogram

mg/l

milligrams per liter

MGD

million gallons per day

MGP

manufactured gas plant

ml

milliliter

mm

millimeter

mM

millimole

MMBtu

million British thermal units

MNSR

minor new source review

MOA

memorandum of agreement

MOBILE

mobile source emission model

MOE

margin of exposure

MOEE

Ontario's Ministry of Environment and Energy

MOU

memorandum of understanding

mp

melting point

MPF

manufacturing process facility

mppcf

million particles per cubic foot

MPTER

Multiple Point Gaussian Dispersion Algorithm with Terrain Adjustment

MRF

materials recovery facility

MSC

medium specific concentration

MSDS

material safety data sheet

msl

mean sea level

MS/Z

multispan / zero box

MTDDIS

mesoscale transport, diffusion and deposition model for industrial sources

MTEC

maximum theoretical emission concentration

MTR

minimum technology requirement

MTR

minimum testing range

MVAPCA

Motor Vehicle Air Pollution Control Act

MVVD

manual vent valve discharge

mw

molecular weight

MWC

municipal waste combuster

MWI

medical waste incinerator

N

NA

nonattainment

NAAQS

National Ambient Air Quality Standards

NAAS

National Air Audit System

NADB

National Atmospheric Data Bank

NADP

National Atmospheric Deposition Program

NAEP

National Association of Environmental Professionals

NAFTA

North American Free Trade Agreement

NAICS

North American Industry Classification System (SIC revision)

NAMA

National Air Monitoring Audits

NAMS

National Air Monitoring System

NAPAP

National Acid Precipitation Assessment Program

NAPBN

National Air Pollution Background Network

NAQTS

National Air Quality Trend Station

NAR

nonattainment review

NARL

National Air and Radiation Laboratory

NARMP

National Acid Rain Monitoring Program

NASN

National Air Surveillance Network

NCAMS

noncontinuous air monitoring station

NCAQ

National Commission on Air Quality

NCAR

National Center for Atmospheric Research

NCEPI

National Center for Environmental Publications and Information

NCO

negotiated consent order

NCP

noncriteria pollutant

NCR

noncompliance report

NCS

National Compliance Strategy

ND

not detected

NDD

negotiated decision document

NDIR

nondispersive infrared analysis

NEA

National Energy Act

NEDA

National Environmental Developmental Association

NEDS

National Emissions Data System (now AIRS)

NEHA

National Environmental Health Association

NEIC

National Enforcement Investigations Center

NEPA

National Environmental Policy Act (42 USC §§ 4321 et seq.)

NEPI

National Environmental Policy Institute

NEPPS

National Environmental Performance Partnership System

NER

National Emissions Report

NERL

National Exposure Research Laboratory

NES

nonopacity emission standards

NESHAPs

national emission standards for hazardous air pollutants (40 CFR pt. 61)

NFA

no further action

NFRAP

no further remedial action planned

ng

nanograms (one billionth of a gram)

NGPA

Natural Gas Policy Act

NICS

National Institute for Chemical Studies

NIEHS

National Institute of Environmental Health Sciences

NIH

National Institute of Health

NIPER

National Institute for Petroleum and Energy Research

NIST

National Institute of Standards and Technology (DOC)

NITEP

National Incinerator Testing and Evaluation Program

NLAP

National Laboratory Audit Program

NLEV

National Low Emission Vehicle program

nm

nanometer

NNC

notice of noncompliance

NNPSPP

National Nonpoint Source Pollution Program

NNSR

non-attainment new source review

NO

nitric oxide

NO2

nitrogen dioxide

NOx

nitrogen oxide

NOAA

National Oceanic and Atmospheric Administration

NOAC

nature of action code

NOAEL

no observed adverse effect level

NOD

notice of deficiency

NODA

notice of data availability

NOE

notice of enforcement

NOEC

no observed effect concentration

NOEL

no observed effect level

NOI

notice of intent

NON

notice of noncompliance

NOO

no odor observed

NOR

notice of registration

NORA

National Occupational Research Agenda

NOS

not otherwise specified

NOT

notice of termination

NOV

notice of violation

NOV/C/D

notice of violation/compliance/demand

NPN

National Particulate Network

NPR

notice of proposed rule making

NPRM

notice of proposed rule making

NPS

National Permit Strategy

NPS

non-point source

NRC

National Research Council

NREP

National Registry of Environmental Professionals

NSF

National Science Foundation

NSPS

new source performance standards

NSR

new source review

NTP

normal temperature and pressure

NTTC

National Technology Transfer Center

NWP

nationwide permit (COE)

NWS

National Weather Service