Division 3.2.2.1 To calculate HC mass emission for compression-ignition engines, the arithmetic average HC concentration shall be calculated using the following equation:

C_{e} = \frac{\int_{t_{1}}^{t_{2}} C_{HC} dt}{t_{2} - t_{1}}

where:

\int_{t_{1}}^{t_{2}} C_{HC} dt

is the integral of the recording of the heated FID over the test (t₁ to t₂);

C_e

is the concentration of HC measured in the diluted exhaust in ppm of C_i and is substituted for C_HC in all relevant equations.