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Converting
Atmospheric Pollutant Concentrations:
from
mg/m3 to ppmv
The conversion factor
depends on the temperature at which you want the conversion
(usually about 20 to 25 degrees Centigrade). At an ambient
pressure of 1 atmosphere, the general equation is:
ppmv
= (mg/m3)(273.15 + °C) / (12.187)(MW)
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where :
mg/ m3: milligrams
of gaseous pollutant per cubic meter of ambient air
MW: molecular
weight of the gaseous pollutant
° C: ambient
air temperature in degrees Centigrade
from
ppmv to mg/m3
The
conversion factor depends on the temperature at which you
want the conversion (usually about 20 to 25 degrees Centigrade).
At an ambient pressure of 1 atmosphere, the general equation
is:
mg/m3
= ( ppmv )(12.187)(MW) / (273.15
+ °C) |
where :
ppmv : ppm by volume
mg/ m3 : milligrams
of gaseous pollutant per cubic meter of ambient air
MW : molecular
weight of the gaseous pollutant
° C : ambient
air temperature in degrees Centigrade
(1)
The pollution laws and regulations in the United
States typically reference their
pollutant limits to an ambient temperature of 20 to 25 °C
as noted above. However, in other nations, the reference
ambient temperature for pollutant limits may be 0 °C
or other values.
(2)
1 percent by volume = 10,000 ppmv (i.e., parts per million
by volume).
Pressure
Conversions:
Atmospheric pressures
may be expressed in a number of different units. The following
table provides the conversions between seven of the most
commonly used units of pressure.
|
atm
|
psi
|
1"
Hg |
kPa
|
Bar
|
mm
Hg |
kg/cm2
|
1
atm = |
1
|
14.6960000
|
29.9212600
|
101.3250000
|
1.0132500
|
760.0000000
|
1.0332280
|
1
psi = |
0.0680460
|
1
|
2.0360210
|
6.8947330
|
0.0689470
|
51.7147500
|
0.0703070
|
1"
Hg = |
0.0334211
|
0.4911541
|
1
|
3.3863880
|
0.0338639
|
25.4000000
|
0.0345316
|
1
kPa = |
0.0098690
|
0.1450380
|
0.2952999
|
1
|
0.0100000
|
7.5006170
|
0.0101970
|
1
bar = |
0.9869230
|
14.5038200
|
29.5299900
|
100.0000000
|
1
|
750.0616000
|
1.0197160
|
1
mm Hg = |
0.0013160
|
0.0193370
|
0.0393701
|
0.1333220
|
0.0013330
|
1
|
0.0013600
|
1
kg/cm2 = |
0.9678410
|
14.2233900
|
0.0028959
|
98.0665000
|
0.9806650
|
735.5590000
|
1
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Although
not included in the above table:
- 1 atmosphere of
pressure = 33.90 feet of water = 10.33 meters of water
- 1 mm Hg = 1 torr
Notes:
atm
= absolute pressure, in atmospheres
psi
= absolute pressure, in pounds per square inch
kPa
= absolute pressure, in kilopascals
bar
= absolute pressure, in bars
mm
Hg = absolute pressure, in millimeters of Mercury
kg/cm2
= absolute pressure, in kilograms
per square centimeter
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