A brief description of the analytical instruments used in this mobile laboratory is presented as follows.
NO/NO2 CEMS (RM 7E) - NOx is measured using a chemiluminescence NO/NO2 gas analyzer. This analyzer measures the intensity of the light given off by the nitric oxide/ozone reaction, where the term chemiluminescence is derived. For measuring NO concentrations only, the gas samples are sent directly to the reaction chamber bypassing the NO2-to-NO converter. For measuring NO2 concentrations, the sample gas passes through a thermal NO2-to-NO converter to convert nitrogen dioxide to nitric oxide and analyze the combined NO/NO2 as NO. The difference of the two measurements, i.e., gases passing through the converter and bypassing the converter, is the NO2 concentration. The instrument is calibrated using zero gas (N2) and EPA Protocol span gas (NO in N2) to ensure data accuracy.
Carbon Monoxide CEMS (RM 10) - Carbon monoxide analysis is accomplished using non- dispersive infrared (NDIR) or gas filter correlation (GFC) analyzers. Both analyzers are precision instruments used for continuous determination of gaseous CO concentrations in streams such as ambient air, stationary source, and vehicle exhaust emissions. The instrument is routinely calibrated using zero gas (N2) and EPA Protocol span gases (CO in N2) at various concentrations.
Excess Oxygen & Carbon Dioxide CEMS (RM 3C) - Oxygen and/or carbon dioxide analyzers are used to automatically and continuously determine the oxygen and/or carbon dioxide contents of gaseous samples. The O2 analyzers have multiple ranges of 0-5%, 0-10%, and/or 0-25% while the CO2 analyzers have multiple ranges of 0-20% and 0-40%. Zero (N2) span gas and EPA Protocol gases (O2 or CO2 in N2) are used for their calibrations.
Sulfur Dioxide CEMS (RM 6C) - SO2 concentrations are measured using a non-dispersive ultraviolet (NDUV) gas analyzer. Its principle of operation is based on the ultraviolet light absorption of the SO2 component in a gas mixture to determine concentrations. The instrument is calibrated using zero gas (N2) and EPA protocol span gases (SO2 in N2) to ensure accuracy.
Total Hydrocarbon (THC) Determination (RM 25A) - For total hydrocarbons (THC) determination, a flame ionization analyzer (FIA) is used to measure total gaseous alkanes, alkenes, and arenes as propane (or other hydrocarbon) equivalence. Methane and ethane concentrations may be excluded by determining their concentrations separately using a gas chromatograph equipped with a flame ionization detector (GC/FID) and deducting their concentrations from the total hydrocarbon concentrations. For most ranges, EPA Protocol gases are used for calibrations.
Data Acquisition System - CEMS data are collected by data acquisition systems (DAS) that include strip-chart recorders and multi-channel/multi-functional data acquisition systems.