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Atmospheric pollutant concentrations expressed as mass per unit volume of atmospheric air (e.g., mg/m 3, μg/m 3, etc.) at sea level will decrease with increasing altitude because the atmospheric pressure decreases with increasing altitude. The change of atmospheric pressure with altitude can be obtained from this equation: [2]
As an example, a measured particulates concentration of 200 mg/m 3 in a dry gas that has a measured 8 volume % CO 2 is: 200 × ( 12 ÷ 8 ) = 300 mg/m 3. when corrected to a dry gas having a specified reference CO 2 content of 12 volume %.
Conversion of units is the conversion of the unit of measurement in which a ... the NO x concentration of 10 ppm v converts to mass flow rate of 24.63 grams ...
Mass; system unit unit-code symbol or abbrev. notes sample default conversion combinations SI: kilogram: kg kg 1.0 kg (2.2 lb) kg lb. kg lb st; kg st. kg st lb; gram: g g
Xchanger Inc, webpage Calculator for SCFM, NM3/hr, lb/hr, kg/hr, ACFM & M3/hr gas flows. onlineflow.de, webpage Online calculator for conversion of volume, mass and molar flows (SCFM, MMSCFD, Nm3/hr, kg/s, kmol/hr and more) ACFM versus SCFM for ASME AG-1 HEPA Filters; SCFM (Standard CFM) vs. ACFM (Actual CFM) (Specifically for air flows only)
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).
The driving force shown here as ' ' is expressed in units of moles per unit of volume, but in some cases the driving force is represented by other measures of concentration with different units. For example, the driving force may be partial pressures when dealing with mass transfer in a gas phase and thus use units of pressure.
In solutions, mass concentration is commonly encountered as the ratio of mass/[volume solution], or m/v. In water solutions containing relatively small quantities of dissolved solute (as in biology), such figures may be "percentivized" by multiplying by 100 a ratio of grams solute per mL solution. The result is given as "mass/volume percentage".