Standards

Air Quality Standards

National Ambient Air Quality Standards (NAAQS)
The NAAQS, as defined in Title 40 of the Code of Federal Regulations, Part 50, provide a basis for evaluating air quality. The primary standards define the levels of air quality necessary to protect the public health with an adequate margin of safety. The secondary standards define levels of air quality necessary to prevent any degradation or harm to the total environment.

 

Carbon Monoxide	Primary: 35 parts per million expressed as the 1-hour concentration; 9 parts per million expressed as the 8-hour concentration. Secondary: same as primary
Lead	Primary: 1.5 micrograms per cubic meter expressed as the quarterly arithmetic mean concentration. Secondary: same as primary
Nitrogen Dioxide	Primary: 0.053 parts per million expressed as the annual arithmetic mean. Secondary: same as primary.
Ozone	Primary: 0.12 parts per million expressed as the hourly average concentration. The 8-hour standard is defined in terms of the daily maximum 8-hour average. Secondary: same as primary.
Particulate Matter 10 Micrometers	Primary: 150 microgram per cubic meters expressed as the 24-hour concentration; 50 micrograms per cubic meter expressed as the annual arithmetic mean concentration. Secondary: same as primary.
Particulate Matter 2.5 Micrometers	Primary: 15 micrograms per cubic meter expressed as the annual arithmetic mean concentration; 65 micrograms per cubic meter expressed as the 24-hour concentration. Secondary: same as primary.
Sulfur Dioxide	Primary: 0.03 parts per million expressed as the annual arithmetic mean; 0.14 parts per million expressed as the maximum 24-hour concentration. Secondary: 0.5 parts per million expressed as the maximum 3-hour concentration.