1.1 This standard is applicable to the determination of nonmethane hydrocarbons (NMHC) in organized emission and fugitive emission of stationary source.
1.2 Detection limit of NMHC is 4×10-3 ng. When chromatogram sample size is 1.0 ml, method detectable concentration is 4×10-2 mg/m3, and the concentration range of method quantitative determination is 0.12 to 32 mg/m3.
2 Definitions
Nonmethane hydrocarbons (NMHC): refers to the generic term for hydrocarbon compounds (mainly of C2 to C8), exclude methane. NMHC measured under the conditions specified in this standard, is the total amount, calculated by carbon content, of hydrocarbon compounds (exclude methane) which have obvious response to the hydrogen flame ionization detector of gas chromatograph.
3 Principle
The total hydrocarbons and methane content in the sample, injected directly by an injector, can be determined respectively by gas chromatograph with dual columns and double hydrogen flame ionization detectors, the nonmethane hydrocarbons content can be obtained from the difference between measured total hydrocarbons and methane content. Simultaneously, the blank value of oxygen shall be determined by hydrocarbon-free air, in order to subtract the oxygen peak interference in the chromatogram peak of total hydrocarbons.
