Various embodiments of the present technology relate to emission monitoring. Some embodiments comprise an exhaust testing system to characterize exhaust gas composition. The exhaust testing system comprises a sampling system and a gas analyzer. The sampling system is coupled to an exhaust stack of a combustion system. The sampling system comprises a cage, sampling pipes, and valves. The cage is mounted to the opening of the exhaust stack. The sampling pipes are mounted to the cage. The sampling pipes capture exhaust gas generated by the combustion system and emitted through the opening of the exhaust stack. The valves control gas flow through the sampling pipes. The gas analyzer is coupled to the sampling pipes. The gas analyzer determines gas composition of the exhaust gas.

A gas analyzer includes a gas flow path through which an analysis target gas flows, and a drain pot upstream of an analysis unit to analyze the gas, the drain pot into which liquid generated by cooling the gas is introduced, wherein the drain pot includes: a first liquid container to receive a terminal end of a first drain flow path from which the liquid is discharged and has a communication port above the terminal end of the first drain flow path; a second drain flow path to extend outward and downward from the communication port of the first liquid container; and a second liquid container to receive a terminal end of the second drain flow path and has a discharge port above the terminal end of the first drain flow path and the terminal end of the second drain flow path, and below the communication port.

Various embodiments include a testing apparatus capable of testing gas flowing in a duct. The apparatus may include: a housing; a sampling tube extending from the housing to be inserted into the duct, the sampling tube including a gas entry channel and a gas exit channel isolated from each other, with a gas inlet of the gas entry channel and a gas outlet of the gas exit channel disposed in a part of the sampling tube leading into the duct and disposed at the same side of the sampling tube, wherein the gas inlet and the gas outlet have matching gas through-flow areas; and a sensor module disposed in the housing and in gas communication with the gas entry channel to test gas sampled from the gas entry channel.

A gas sampling apparatus including a housing having a housing wall and a housing opening. The gas sampling apparatus includes a sample system for extracting the gaseous sample, including a sample pipe having an opening enclosed by the housing wall and in fluid communication with the gaseous environment and filter means including a filter for filtering solid particles from the gaseous sample. The filter is enclosed by the housing wall and arranged at the opening. The gas sampling apparatus includes a central purge system to remove aggregates of solid particles deposited on one or more housing surfaces by a gaseous medium, wherein the central purge system includes a purge pipe including an outlet opening directed towards the housing opening and enclosed by the housing wall, wherein the sample system is arranged externally to the central purge system so that the sample pipe is separate from the purge pipe.