Section 243.101  Definitions

For the purposes of this Part, terms listed below will have the meanings attributed to them in this Section.  As used in this Part, all terms not defined in this Section will have the meaning given them by the Act; the CAA, incorporated by reference in Section 243.108; or 35 Ill. Adm. Code 201.102.

"Act" means the Environmental Protection Act [415 ILCS 5].

"Agency" means the Illinois Environmental Protection Agency.

"Ambient air" means that portion of the atmosphere, external to buildings, to which the general public has access.

"Clean Air Act" or "CAA" means the federal Clean Air Act (42 USC 7401 et seq., as amended), incorporated by reference in Section 243.108.

"Exceedance of a NAAQS" means one occurrence of a measured or modeled concentration that exceeds the specified concentration level of that NAAQS for the averaging period specified by the standard.

"Exceptional event" means an event and its resulting emissions that fulfills all of the following criteria:

The event affects air quality in such a way that there exists a clear causal relationship between the specific event and the monitored exceedance or violation;

The event is not reasonably controllable or preventable;

The event is caused by human activity that is unlikely to recur at a particular location or a natural event; and

The event is determined by USEPA in accordance with 40 CFR 50.14 to be an exceptional event.

An "exceptional event" does not include any of the following:

Air pollution relating to source noncompliance;

Stagnation of air masses and meteorological inversions;

A meteorological event involving high temperatures or lack of precipitation (i.e., severe, extreme or exceptional drought).

BOARD NOTE:  Stagnation of air masses, meteorological inversions, and meteorological events involving high temperatures or lack of precipitation do not directly cause pollutant emissions and are not exceptional events.  However, conditions involving high temperatures or lack of precipitation may promote occurrences of particular types of exceptional events, such as wildfires or high wind events, that do directly cause emissions.

"Federal equivalent method" or "FEM" means a method for measuring the concentration of an air pollutant in the ambient air that USEPA has designated as an equivalent method pursuant to 40 CFR 53 and that is included in the List of Designated Methods, including later updates, as incorporated by reference in Section 243.108; the term "federal equivalent method" does not include a method for which USEPA has cancelled or superseded an equivalent method designation in accordance with 40 CFR 53.11 or 53.16, as reflected in the incorporation by reference in Section 243.108.

BOARD NOTE:  Derived from 40 CFR 50.1(f) (definition of "equivalent method"), 50.11(d)(2) (parenthetical definition of "FEM"), and 53.1 (definition of "federal equivalent method").  The clause "including later updates" in this definition is intended to exclude methods canceled by USEPA pursuant to 40 CFR 53.11 or 53.16 for which the cancellation is included in the updates to List of Designated Methods incorporated by reference in Section 243.108.  A federal designation of an FEM becomes effective upon publication of a notice in the Federal Register.  A federal cancellation of an FEM becomes effective upon deletion from the listing of FEMs.

"Federal land manager" means the Secretary of the department with authority over the federal Class I area (or the Secretary's designee).

BOARD NOTE:  See 40 CFR 50.1(r) and 51.301 (definitions of "federal land manager").  There are no federal Class I areas in or immediately abutting Illinois.  See subpart D of 40 CFR 81.

"Federal reference method" or "FRM" means a method of sampling and analyzing the ambient air for an air pollutant that USEPA has specified as a reference method in an appendix to 40 CFR 50, incorporated by reference in Section 243.108, or a method that USEPA has designated as a reference method pursuant to 40 CFR 53 and that is included in List of Designated Methods, including later updates, incorporated by reference in Section 243.108; the term "federal reference method" does not include a method for which USEPA has cancelled or superseded a reference method designation in accordance with 40 CFR 53.11 or 53.16, as reflected in the incorporation by reference in Section 243.108.

BOARD NOTE:  Derived from 40 CFR 50.1(f) (definition of "reference method") and 53.1 (definition of "federal reference method").  The clause "including later updates" in this definition is intended to include methods canceled by USEPA pursuant to 40 CFR 53.11 or 53.16 for which the cancellation is included in the updates to List of Designated Methods incorporated by reference in Section 243.108.  A federal designation of an FRM becomes effective upon publication of a notice in the Federal Register.  A federal cancellation of an FRM becomes effective upon deletion from the listing of FRMs or from an appendix to 40 CFR 50.

"High wind dust event" is an event that includes the high-speed wind and the dust that the wind entrains and transports to a monitoring site.

"High wind threshold" is the minimum wind speed capable of causing particulate matter emissions from natural undisturbed lands in the area affected by a high wind dust event.

"Micrograms per cubic meter" or "µg/m³" means one millionth (10^‑6) of a gram of a contaminant per cubic meter of ambient air, as measured and determined by the methods prescribed for that contaminant.

BOARD NOTE:  The Board added this definition and that for "milligrams per liter".

"Milligrams per cubic meter" or "mg/m³" means one thousandth (10^‑3) of a gram of a contaminant per cubic meter of ambient air, as measured and determined by the methods prescribed for that contaminant.

"National Ambient Air Quality Standard" or "NAAQS" means a standard established by USEPA that applies for outdoor air throughout the United States.

BOARD NOTE:  The Board added this definition, derived from the definition in "Terms of Environment:  Glossary, Abbreviations, and Acronyms" (December 1997), EPA 175-B-97-001, at p. 30.  USEPA has codified the NAAQS at 40 CFR 50.

BOARD NOTE:  The Board added this definition based on the definition in "Terms of Environment:  Glossary, Abbreviations, and Acronyms" (December 1997), document number EPA 175-B-97-001, USEPA, Office of Communications, Education, and Public Affairs, at p. 30.

"Natural event" means an event and its resulting emissions, which may recur at the same location, in which human activity plays little or no direct causal role. For purposes of this definition, anthropogenic sources that are reasonably controlled are not human activity that plays a direct causal role in causing emissions.

"Parts per billion" or "ppb" means the ratio of the parts of a specified contaminant to a billion parts of air by weight (1:10^‑9), as measured and determined by the methods prescribed for that contaminant.

BOARD NOTE:  The Board added this definition and that for "parts per million", derived from the parentheticals in 40 CFR 50.4(a) and (b) and 50.17(a) and the definition of "parts per billion (ppb)/parts per million (ppm)" in "Terms of Environment:  Glossary, Abbreviations, and Acronyms" (December 1997), EPA 175-B-97-001, at p. 34.

"Parts per million" or "ppm" means the ratio of the parts of a specified contaminant to a million parts of air by weight (1:10^‑6), as measured and determined by the methods prescribed for that contaminant.

BOARD NOTE:  The Board added this definition, derived from the parentheticals in 40 CFR 50.4(a) and (b) and 50.17(a) and the definition of "parts per billion (ppb)/parts per million (ppm)" in "Terms of Environment:  Glossary, Abbreviations, and Acronyms" (December 1997), EPA 175-B-97-001, at p. 34.

"PM₁₀" means particulate matter that has an aerodynamic diameter less than or equal to a nominal 10 micrometers (µm).

BOARD NOTE:  The Board added this definition, derived from the parenthetical definition in 40 CFR 50.6(c).

"PM_2.5" means particulate matter that has an aerodynamic diameter less than or equal to a nominal 2.5 micrometers (µm).

BOARD NOTE:  The Board added this definition, derived from the parenthetical definition in 40 CFR 50.7(a).

"Prescribed fire" is any fire intentionally ignited by management actions in accordance with applicable laws, policies, and regulations to meet specific land or resource management objectives.

"Traceable" means that a local standard has been compared and certified either directly or via not more than one intermediate standard, to a primary standard, such as a National Bureau of Standards Standard Reference Material (NBS SRM), or a USEPA/NBS-approved Certified Reference Material (CRM).

"USEPA" means the United States Environmental Protection Agency.

BOARD NOTE:  Derived from 40 CFR 50.1(c).  The Board has used "USEPA" in text where USEPA has used "Administrator", if action by USEPA is clearly contemplated.  Otherwise, the Board has retained the term "Agency" as defined in this Section.

"Wildfire" is any fire started by an unplanned ignition caused by lightning; volcanoes; other acts of nature; unauthorized activity; or accidental, human-caused actions, or a prescribed fire that has developed into a wildfire.  A wildfire that predominantly occurs on wildland is a natural event.

"Wildland" means an area in which human activity and development are essentially non-existent, except for roads, railroads, power lines, and similar transportation facilities.  Structures, if any, are widely scattered.

BOARD NOTE:  Derived from 40 CFR 50.1 (2016), except as otherwise more specifically indicated.

(Source:  Amended at 45 Ill. Reg. 337, effective December 17, 2020)