PRODUCT INFORMATION
INDEX
DATE
Dep.2
IC-C-D-40-001e C
November 2015
EMISSION UNITS CONVERSION
1/3
1. EMISSION UNITS CONVERSION
For further information on emission computation and units conversion, refer to ISO 8178-1 (2006).
Exhaust emissions are usually stated in any of the following units:
Parts per million
- ppm
(1)
Milligrams per cubic meter (normal)
- mg/m
n
3
(2)
Grams per kilowatt-hour
- g/kWh
Generally analyzers measure volume, in ppm or %, in wet basis (considering the water of the exhaust gases) or
in dry basis (water not considered). Some analyzers can give results in other units after making internal
calculations.
In case of mg/m3 units, the pressure and temperature conditions as reference must be taken into account. This
can suppose differences between the values from different equipments. To compare different equipments
measurement in this unit, they have to reference to the same pressure and temperature conditions. Legislations
use to indicate the reference conditions to be taken. In general normal conditions, 0ºC and 1013 mbar (100 KPa)
are the usual reference.
Below are bases of unit conversion for a number of components:
1.1. Converting
ppm to mg/m
n
3 (
2)
Multiply the ppm value by the density of the gas to be measured under normal conditions
(
2)
, which is, in kg/m
n
3
:
Nitrogen Oxides, NOx such as NO
2
2.053
Sulfur Dioxide, SO
2
2.85
Carbon monoxide, CO
1.250
Total Hydrocarbon, THC (C/H RATIO 1.85) 0.619 (0.716 in case of natural gas)
Methane, CH
4
0.716
Formaldehyde, CH
2
O
1.34
NMHC (Non Methane HydroCarbons) are calculated by subtracting CH4 (methane) from THC (Total
HydroCarbons).
When measuring ppm or mg/Nm
3
, the usual practice is to take a reference exhaust oxygen value; in this event,
the result must be multiplied by:
20.95 - O
2
ref
(%)
-----------------------------
20.95 - O
2
measured (%)
Generally, the most frequent O
2
ref
(%) values are 3, 5, 7, 12 and 15, and they are specified by the applicable
legislation.
(1) Parts per milion by volume, sometimes noted ppmv, 1 ppm = 0.0001%
(2) (Normal conditions: Temperature 273 K and Pressure 1013 mbar)
4.1.45
O&M_2.002211.810_A_10_2016
