Air quality

Scope

The national ambient air quality standards (NAAQS) are the limit levels of “criteria pollutants,” which include:

1. Carbon monoxide
2. Lead
3. Nitrogen dioxide
4. Particulate matter
5. Ozone
6. Sulfur dioxide

One of the primary goals of the NAAQS standards is to encourage or otherwise promote reasonable federal, state, and local governmental actions for pollution prevention.

Under the CAA, EPA is required to revise the NAAQS for each of the criteria pollutants every five years.

Regulatory citations

• 40 CFR Part 50 — National Primary and Secondary Ambient Air Quality Standards

Key definitions

• Affected facility: With reference to a stationary source, any apparatus to which a standard is applicable.
• Ambient air: That portion of the atmosphere, external to buildings, to which the general public has access.
• Approved permit program: A state permit program approved by the Administrator as meeting the requirements of part 70 of this chapter or a Federal permit program established in this chapter pursuant to Title V of the Act (42 U.S.C. 7661).
• Construction: Fabrication, erection, or installation of an affected facility.
• Continuous monitoring system: The total equipment, required under the emission monitoring sections in applicable subparts, used to sample and condition (if applicable), to analyze, and to provide a permanent record of emissions or process parameters.
• Electric utility steam generating unit: Any steam electric generating unit that is constructed for the purpose of supplying more than one-third of its potential electric output capacity and more than 25 MW electrical output to any utility power distribution system for sale. Any steam supplied to a steam distribution system for the purpose of providing steam to a steam-electric generator that would produce electrical energy for sale is also considered in determining the electrical energy output capacity of the affected facility.
• Exceedance: With respect to a national ambient air quality standard means one occurrence of a measured or modeled concentration that exceeds the specified concentration level of such standard for the averaging period specified by the standard.
• Exceptional event: An event(s) and its resulting emissions that affect air quality in such a way that there exists a clear causal relationship between the specific event(s) and the monitored exceedance(s) or violation(s), is not reasonably controllable or preventable, is an event(s) caused by human activity that is unlikely to recur at a particular location or a natural event(s), and is determined by the Administrator in accordance with 40 CFR 50.14 to be an exceptional event. It does not include air pollution relating to source noncompliance. Stagnation of air masses and meteorological inversions do not directly cause pollutant emissions and are not exceptional events. Meteorological events involving high temperatures or lack of precipitation (i.e., severe, extreme or exceptional drought) also do not directly cause pollutant emissions and are not considered 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, which do directly cause emissions.
• Existing facility: With reference to a stationary source, any apparatus of the type for which a standard is promulgated in this part, and the construction or modification of which was commenced before the date of proposal of that standard; or any apparatus which could be altered in such a way as to be of that type.
• High wind dust event: An event that includes the high-speed wind and the dust that the wind entrains and transports to a monitoring site.
• Malfunction: Any sudden, infrequent, and not reasonably preventable failure of air pollution control equipment, process equipment, or a process to operate in a normal or usual manner. Failures that are caused in part by poor maintenance or careless operation are not malfunctions.
• Modification: Any physical change in, or change in the method of operation of, an existing facility which increases the amount of any air pollutant (to which a standard applies) emitted into the atmosphere by that facility or which results in the emission of any air pollutant (to which a standard applies) into the atmosphere not previously emitted.
• Nitrogen oxides: All oxides of nitrogen except nitrous oxide, as measured by test methods set forth in this part.
• Opacity: The degree to which emissions reduce the transmission of light and obscure the view of an object in the background.
• Particulate matter: Any finely divided solid or liquid material, other than uncombined water, as measured by the reference methods specified under each applicable subpart, or an equivalent or alternative method.
• Reference method: Any method of sampling and analyzing for an air pollutant as specified in the applicable subpart.
• Shutdown: The cessation of operation of an affected facility for any purpose.
• Startup: The setting in operation of an affected facility for any purpose.
• Stationary source: Any building, structure, facility, or installation which emits or may emit any air pollutant.
• Title V permit: Any permit issued, renewed, or revised pursuant to Federal or State regulations established to implement title V of the Act (42 U.S.C. 7661). A title V permit issued by a State permitting authority is called a part 70 permit in this part.
• Volatile Organic Compound (VOC): Any organic compound which participates in atmospheric photochemical reactions; or which is measured by a reference method, an equivalent method, an alternative method, or which is determined by procedures specified under any subpart.

Summary of requirements

• Understand if your facility is a stationary source that emits one of the six “criteria pollutants,” which are:
  • Carbon monoxide
  • Nitrogen dioxide
  • Particulate matter
  • Ozone
  • Sulfur dioxide
  • Lead
• Contact your state to begin the air permitting process for new construction or significant modifications to your facility or new operations that will affect your facility’s emissions to the air.