The EPA Air Quality Standard (NAAQS) for carbon monoxide is 9 parts per million. Carbon monoxide (CO) is both an asphyxiant gas and an indicator of the presence of other combustion-related vapors. Elevated levels of carbon monoxide generally result from defective combustion exhaust systems, automotive exhaust, and tobacco smoke. CO levels may vary widely from day to day and hour to hour. For premises heated with gas or oil, CO levels should always be checked during cold weather with the heating systems on to be certain that the combustion exhaust system is functioning properly. Symptoms resulting from CO exposure may include headache, dizziness, confusion, nausea and fatigue. Carbon Monoxide Air Quality Standards vary from country to country.
The EPA air quality standard for particulate matter (PM 2.5) in air is 12 micrograms per cubic meter (μg/m3).
PM stands for particulate matter (also called particle pollution): the term for a mixture of solid particles and liquid droplets found in the air. Some particles, such as dust, dirt, soot, or smoke, are large or dark enough to be seen with the naked eye. Others are so small they can only be detected using an electron microscope.
Particle pollution includes:
EPA Air Quality Sources of PM 2.5
- PM10 : inhalable particles, with diameters that are generally 10 micrometers and smaller; and
- PM2.5 : fine inhalable particles, with diameters that are generally 2.5 micrometers and smaller.
- How small is 2.5 micrometers? Think about a single hair from your head. The average human hair is about 70 micrometers in diameter – making it 30 times larger than the largest fine particle.
These particles come in many sizes and shapes and can be made up of hundreds of different chemicals.
Some are emitted directly from a source, such as construction sites, unpaved roads, fields, smokestacks or fires.
Most particles form in the atmosphere as a result of complex reactions of chemicals such as sulfur dioxide and nitrogen oxides, which are pollutants emitted from power plants, industries and automobiles.
On December 14, 2012, EPA finalized an update to the National Ambient EPA Air Quality Standard for PM2.5. The annual standard was reduced from 15 μg/m3 to 12 μg/m3. The daily PM2.5 standard and standards for PM10 were retained. The revised 2012 PM standard became effective on March 18, 2013.