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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.
A normal cubic meter (Nm 3) is the metric expression of gas volume at standard conditions and it is usually (but not always) defined as being measured at 0 °C and 1 atmosphere of pressure. A standard cubic foot (scf) is the USA expression of gas volume at standard conditions and it is often ( but not always ) defined as being measured at 60 ...
Criteria can be set in different units (e.g. μg/m 3, parts per billion by volume (ppbv), parts per billion by mass (ppb (mass)), parts per million (ppm)) and it is possible to convert between all of these units if the molecular mass of the pollutant and the temperature are known. Different standard temperatures are used throughout the world ...
The amount of pollutant present in air is usually expressed as a concentration, measured in either parts-per notation (usually parts per billion, ppb, or parts per million, ppm, also known as the volume mixing ratio), or micrograms per cubic meter (μg/m³).
In fractions like "2 nanometers per meter" (2 n m / m = 2 nano = 2×10 −9 = 2 ppb = 2 × 0.000 000 001), so the quotients are pure-number coefficients with positive values less than or equal to 1. When parts-per notations, including the percent symbol (%), are used in regular prose (as opposed to mathematical expressions), they are still pure ...
10 −1: dM: 140 mM: sodium ions in blood plasma [10] 480 mM: sodium ions in seawater [20] 10 0: M: 1 M: standard state concentration for defining thermodynamic activity [21] 10 1: daM 17.5 M pure (glacial) acetic acid (1.05 g/cm 3) [22] 40 M: pure solid hydrogen (86 g/L) [23] 55.5 M: pure water at 3.984 °C, temperature of its maximum density ...
For ozone (O 3), the guidelines suggest values no higher than 100 μg/m 3 for an 8-hour mean and 60 μg/m 3 peak season mean. [2] For nitrogen dioxide (NO 2), the guidelines set 10 μg/m 3 for the annual mean or 25 μg/m 3 for a 24-hours mean. [2] For sulfur dioxide (SO 2), the guidelines stipulate concentrations not exceeding 40 μg/m 3 24 ...
0.12 ppm 1 year 0.03 ppm Ozone 1 hour 0.10 ppm 4 hours 0.08 ppm Sulfur dioxide 1 hour 0.20 ppm 1 day 0.08 ppm 1 year 0.02 ppm Lead 1 year 0.50 μg/m 3: PM 10 1 day 50 μg/m 3: 1 year 25 μg/m 3: PM 2.5 1 day 25 μg/m 3: 1 year 8 μg/m 3