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These units express the concentration of air pollution in terms of the mass or volume of the pollutant, and they are commonly used for measurements of both gaseous pollutants, such as nitrogen dioxide, and coarse (PM 10) and fine (PM 2.5) particulates.
As an example, a measured NO x concentration of 45 ppmv in a dry gas having 5 volume % O 2 is: 45 × ( 20.9 - 3 ) ÷ ( 20.9 - 5 ) = 50.7 ppmv of NO x. when corrected to a dry gas having a specified reference O 2 content of 3 volume %. Note: The measured gas concentration C m must first be corrected to a dry basis before using the above equation.
Particulate matter (PM) is generally classified into two main size categories: PM 10 and PM 2.5. PM 10, also known as coarse particulate matter, consists of particles 10 micrometers (μm) and smaller, while PM 2.5, also called fine particulate matter, consists of particles 2.5 μm and smaller. [29]
The CCME standard for particulate matter 2.5 (PM 2.5) as of 2015 is 28 μg/m 3 (calculated using the 3-year average of the annual 98th percentile of the daily 24-hr average concentrations) and 10 μg/m 3 (3-year average of annual mean). PM 2.5 standards will increase in stringency in 2020. [273]
Quantities, Units and Symbols in Physical Chemistry, also known as the Green Book, is a compilation of terms and symbols widely used in the field of physical chemistry. It also includes a table of physical constants , tables listing the properties of elementary particles , chemical elements , and nuclides , and information about conversion ...
Source term (the concentration or quantity of toxins in emission or accidental release source terms) and temperature of the material Emissions or release parameters such as source location and height, type of source (i.e., fire, pool or vent stack) and exit velocity , exit temperature and mass flow rate or release rate.
One day of exposure to PM2.5 at a concentration of 880 μg/m 3, such as occurs in Beijing, China, is the equivalent of smoking one or two cigarettes in terms of particulate inhalation by weight. [ 25 ] [ 26 ] The analysis is complicated, however, by the fact that the organic compounds present in various ambient particulates may have a higher ...
The score for each pollutant is non-linear, as is the final AQI score. Thus an AQI of 300 does not mean twice the pollution of AQI at 150, nor does it mean the air is twice as harmful. The concentration of a pollutant when its IAQI is 100 does not equal twice its concentration when its IAQI is 50, nor does it mean the pollutant is twice as harmful.