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The concentrations of carbon dioxide in the atmosphere are expressed as parts per million by volume (abbreviated as ppmv, or ppm(v), or just ppm). To convert from the usual ppmv units to ppm mass (abbreviated as ppmm, or ppm(m)), multiply by the ratio of the molar mass of CO 2 to that of air, i.e. times 1.52 (44.01 divided by 28.96).
Air quality is acceptable; however, for some pollutants there may be a moderate health concern for a very small number of people who are unusually sensitive to air pollution. Unusually sensitive people: Consider reducing prolonged or heavy exertion. Watch for symptoms such as coughing or shortness of breath. These are signs to take it easier.
Some express the concentrations as ppmv (parts per million by volume) and some express the concentrations as mg/m 3 (milligrams per cubic meter), while others require adjusting or correcting the concentrations to reference conditions of moisture content, oxygen content or carbon dioxide content.
Carbon dioxide concentrations in closed or confined rooms can increase to 1,000 ppm within 45 minutes of enclosure. For example, in a 3.5-by-4-metre (11 ft × 13 ft) sized office, atmospheric carbon dioxide increased from 500 ppm to over 1,000 ppm within 45 minutes of ventilation cessation and closure of windows and doors. [93]
The primary standard was set at 9 ppm averaged over an 8-hour period and 35 ppm over a 1-hour period. [10] The majority of CO emitted into the ambient air is from mobile sources. The EPA has reviewed and assessed the current scientific literature with respect to CO in 1979, 1984, 1991, and 1994. [11]
The World Health Organization guidelines were most recently updated in 2021. [1] The guidelines offer guidance about these air pollutants: particulate matter (PM), ozone (O 3), nitrogen dioxide (NO 2), sulfur dioxide (SO 2) and carbon monoxide (CO). [2]
Emission standards are the legal requirements governing air pollutants released into the atmosphere.Emission standards set quantitative limits on the permissible amount of specific air pollutants that may be released from specific sources over specific timeframes.
Carbon dioxide is soluble in water and is found in groundwater, lakes, ice caps, and seawater. It is a trace gas in Earth's atmosphere at 421 parts per million (ppm) [a], or about 0.042% (as of May 2022) having risen from pre-industrial levels of 280 ppm or about 0.028%.