{"data":{"id":"us/40-cfr-53.1","jurisdiction":"us","citation":"40 CFR 53.1","heading":"Definitions.","body":"Terms used but not defined in this part shall have the meaning given them by the Act.\nAct means the Clean Air Act (42 U.S.C. 1857-1857l), as amended.\nAdditive and multiplicative bias means the linear regression intercept and slope of a linear plot fitted to corresponding candidate and reference method mean measurement data pairs.\nAdministrator means the Administrator of the Environmental Protection Agency (EPA) or his or her authorized representative.\nAgency means the Environmental Protection Agency.\nApplicant means a person or entity who submits an application for a Federal reference method or Federal equivalent method determination under § 53.4, or a person or entity who assumes the rights and obligations of an applicant under § 53.7. Applicant may include a manufacturer, distributor, supplier, or vendor.\nAutomated method or analyzer means a method for measuring concentrations of an ambient air pollutant in which sample collection (if necessary), analysis, and measurement are performed automatically by an instrument.\nCandidate method means a method for measuring the concentration of an air pollutant in the ambient air for which an application for a Federal reference method determination or a Federal equivalent method determination is submitted in accordance with § 53.4, or a method tested at the initiative of the Administrator in accordance with § 53.7.\nClass I equivalent method means an equivalent method for PM 2.5 or PM 10-2.5 which is based on a sampler that is very similar to the sampler specified for reference methods in appendix L or appendix O (as applicable) of part 50 of this chapter, with only minor deviations or modifications, as determined by EPA.\nClass II equivalent method means an equivalent method for PM 2.5 or PM 10-2.5 that utilizes a PM 2.5 sampler or PM 10-2.5 sampler in which integrated PM 2.5 samples or PM 10-2.5 samples are obtained from the atmosphere by filtration and subjected to a subsequent filter conditioning process followed by a gravimetric mass determination, but which is not a Class I equivalent method because of substantial deviations from the design specifications of the sampler specified for reference methods in appendix L or appendix O (as applicable) of part 50 of this chapter, as determined by EPA.\nClass III equivalent method means an equivalent method for PM 2.5 or PM 10-2.5 that is an analyzer capable of providing PM 2.5 or PM 10-2.5 ambient air measurements representative of one-hour or less integrated PM 2.5 or PM 10-2.5 concentrations as well as 24-hour measurements determined as, or equivalent to, the mean of 24 one-hour consecutive measurements.\nCO means carbon monoxide.\nCollocated means two or more air samplers, analyzers, or other instruments that are operated simultaneously while located side by side, separated by a distance that is large enough to preclude the air sampled by any of the devices from being affected by any of the other devices, but small enough so that all devices obtain identical or uniform ambient air samples that are equally representative of the general area in which the group of devices is located.\nFederal equivalent method (FEM) means a method for measuring the concentration of an air pollutant in the ambient air that has been designated as an equivalent method in accordance with this part; it does not include a method for which an equivalent method designation has been canceled in accordance with § 53.11 or § 53.16.\nFederal reference method (FRM) means a method of sampling and analyzing the ambient air for an air pollutant that is specified as a reference method in an appendix to part 50 of this chapter, or a method that has been designated as a reference method in accordance with this part; it does not include a method for which a reference method designation has been canceled in accordance with § 53.11 or § 53.16.\nISO 9001-registered facility means a manufacturing facility that is either:\n(1) An International Organization for Standardization (ISO) 9001-registered manufacturing facility, registered to the ISO 9001 standard (by the Registrar Accreditation Board (RAB) of the American Society for Quality Control (ASQC) in the United States), with registration maintained continuously; or\n(2) A facility that can be demonstrated, on the basis of information submitted to the EPA, to be operated according to an EPA-approved and periodically audited quality system which meets, to the extent appropriate, the same general requirements as an ISO 9001-registered facility for the design and manufacture of designated Federal reference method and Federal equivalent method samplers and monitors.\nISO-certified auditor means an auditor who is either certified by the Registrar Accreditation Board (in the United States) as being qualified to audit quality systems using the requirements of recognized standards such as ISO 9001, or who, based on information submitted to the EPA, meets the same general requirements as provided for ISO-certified auditors.\nManual method means a method for measuring concentrations of an ambient air pollutant in which sample collection, analysis, or measurement, or some combination thereof, is performed manually. A method for PM 10 or PM 2.5 which utilizes a sampler that requires manual preparation, loading, and weighing of filter samples is considered a manual method even though the sampler may be capable of automatically collecting a series of sequential samples.\nNO means nitrogen oxide.\nNO2 means nitrogen dioxide.\nNOX means oxides of nitrogen and is defined as the sum of the concentrations of NO2 and NO.\nO3 means ozone.\nOperated simultaneously means that two or more collocated samplers or analyzers are operated concurrently with no significant difference in the start time, stop time, and duration of the sampling or measurement period.\nPb means lead.\nPM means PM 10, PM 10C, PM 2.5, PM 10-2.5, or particulate matter of unspecified size range.\nPM2.5 means particulate matter with an aerodynamic diameter less than or equal to a nominal 2.5 micrometers as measured by a reference method based on appendix L of part 50 of this chapter and designated in accordance with part 53 of this chapter, by an equivalent method designated in accordance with part 53 of this chapter, or by an approved regional method designated in accordance with appendix C to this part.\nPM10 means particulate matter with an aerodynamic diameter less than or equal to a nominal 10 micrometers as measured by a reference method based on appendix J of part 50 of this chapter and designated in accordance with this part or by an equivalent method designated in accordance with this part.\nPM10C means particulate matter with an aerodynamic diameter less than or equal to a nominal 10 micrometers as measured by a reference method based on appendix O of part 50 of this chapter and designated in accordance with this part or by an equivalent method designated in accordance with this part.\nPM10-2.5 means particulate matter with an aerodynamic diameter less than or equal to a nominal 10 micrometers and greater than a nominal 2.5 micrometers as measured by a reference method based on appendix O to part 50 of this chapter and designated in accordance with this part or by an equivalent method designated in accordance with this part.\nPM2.5 sampler means a device, associated with a manual method for measuring PM 2.5, designed to collect PM 2.5 from an ambient air sample, but lacking the ability to automatically analyze or measure the collected sample to determine the mass concentrations of PM 2.5 in the sampled air.\nPM10 sampler means a device, associated with a manual method for measuring PM 10, designed to collect PM 10 from an ambient air sample, but lacking the ability to automatically analyze or measure the collected sample to determine the mass concentrations of PM 10 in the sampled air.\nPM10C sampler means a PM 10 sampler that meets the special requirements for a PM 10C sampler that is part of a PM 10-2.5 reference method sampler, as specified in appendix O to part 50 of this chapter, or a PM 10 sampler that is part of a PM 10-2.5 sampler that has been designated as an equivalent method for PM 10-2.5.\nPM10-2.5 sampler means a sampler, or a collocated pair of samplers, associated with a manual method for measuring PM 10-2.5 and designed to collect either PM 10-2.5 directly or PM 10C and PM 2.5 separately and simultaneously from concurrent ambient air samples, but lacking the ability to automatically analyze or measure the collected sample(s) to determine the mass concentrations of PM 10-2.5 in the sampled air.\nSequential samples for PM samplers means two or more PM samples for sequential (but not necessarily contiguous) time periods that are collected automatically by the same sampler without the need for intervening operator service.\nSO2 means sulfur dioxide.\nTest analyzer means an analyzer subjected to testing as part of a candidate method in accordance with subparts B, C, D, E, or F of this part, as applicable.\nTest sampler means a PM 10 sampler, PM 2.5 sampler, or PM 10-2.5 sampler subjected to testing as part of a candidate method in accordance with subparts C, D, E, or F of this part.\nUltimate purchaser means the first person or entity who purchases a Federal reference method or a Federal equivalent method for purposes other than resale.","path":["Title 40—Protection of Environment","CHAPTER I—ENVIRONMENTAL PROTECTION AGENCY","SUBCHAPTER C—AIR PROGRAMS","PART 53—AMBIENT AIR MONITORING REFERENCE AND EQUIVALENT METHODS","Subpart A—General Provisions"],"source_url":"https://www.ecfr.gov/api/versioner/v1/full/2026-08-25/title-40.xml","current_through":"2026-08-25","vintage":"","retrieved_at":"2026-08-27T02:26:04Z","sha256":"36b622632dca80da93dc5974c53c462df24bbc20782731c42e72db95836f4706","source_id":"us-cfr","stale":true,"prev":"us/40-cfr-appendix-f-to-part-52","next":"us/40-cfr-53.2"},"notice":"GroundRules: Original legal text. Not legal advice."}