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  2. Parts-per notation - Wikipedia

    en.wikipedia.org/wiki/Parts-per_notation

    For example, the conversion factor between a mass fraction of 1 ppb and a mole fraction of 1 ppb is about 4.7 for the greenhouse gas CFC-11 in air (Molar mass of CFC-11 / Mean molar mass of air = 137.368 / 28.97 = 4.74). For volume fraction, the suffix "V" or "v" is sometimes appended to the parts-per notation (e.g. ppmV, ppbv, pptv).

  3. Air pollutant concentrations - Wikipedia

    en.wikipedia.org/wiki/Air_pollutant_concentrations

    1 atm = absolute pressure of 101.325 kPa or 1.01325 bar; mol = gram mole and kmol = 1000 gram moles; Pollution regulations in the United States typically reference their pollutant limits to an ambient temperature of 20 to 25 °C as noted above. In most other nations, the reference ambient temperature for pollutant limits may be 0 °C or other ...

  4. Useful conversions and formulas for air dispersion modeling

    en.wikipedia.org/wiki/Useful_conversions_and...

    Wind speed conversion factors. Meteorological data includes wind speeds which may be expressed as statute miles per hour, knots, or meters per second. Here are the conversion factors for those various expressions of wind speed: 1 m/s = 2.237 statute mile/h = 1.944 knots. 1 knot = 1.151 statute mile/h = 0.514 m/s.

  5. National Ambient Air Quality Standards - Wikipedia

    en.wikipedia.org/wiki/National_Ambient_Air...

    1-hour Not to be exceeded more than once per year 40 CFR 50.8: Primary 9 ppm (10 mg/m 3) 8-hour Not to be exceeded more than once per year 40 CFR 50.8: Ozone (O 3) Primary and Secondary 0.12 ppm (235 μg/m 3) 1-hour a: expected number of days per calendar year, with maximum hourly average concentration greater than 0.12 ppm, is equal to or less ...

  6. Lead - Wikipedia

    en.wikipedia.org/wiki/Lead

    Lead (pronounced "led") is a chemical element; it has symbol Pb (from Latin plumbum) and atomic number 82. It is a heavy metal that is denser than most common materials. Lead is soft and malleable, and also has a relatively low melting point. When freshly cut, lead is a shiny gray with a hint of blue.

  7. Greenhouse gas - Wikipedia

    en.wikipedia.org/wiki/Greenhouse_gas

    This is an accepted version of this page This is the latest accepted revision, reviewed on 8 November 2024. Gas in an atmosphere with certain absorption characteristics This article is about the physical properties of greenhouse gases. For how human activities are adding to greenhouse gases, see Greenhouse gas emissions. Greenhouse gases trap some of the heat that results when sunlight heats ...

  8. Median lethal dose - Wikipedia

    en.wikipedia.org/wiki/Median_lethal_dose

    Median lethal dose. In toxicology, the median lethal dose, LD50 (abbreviation for " lethal dose, 50%"), LC50 (lethal concentration, 50%) or LCt50 is a toxic unit that measures the lethal dose of a given substance. [1] The value of LD 50 for a substance is the dose required to kill half the members of a tested population after a specified test ...

  9. Trichloroethylene - Wikipedia

    en.wikipedia.org/wiki/Trichloroethylene

    Average TCE concentrations measured in air across the United States are generally between 0.01 ppb and 0.3 ppb, although mean levels as high as 3.4 ppb have been reported. [43] TCE levels in the low parts per billion range have been measured in food; however, levels as high as 140 ppb were measured in a few samples of food. [ 43 ]