Low Level Particulate Matter Compliance Issue


During a routine periodic test, our client was unable to demonstrate compliance of a PM10 emission limit on a unit at a gas fired combustion turbine electric generator. Units like these are often subjected to emission limits that tax the equipment and skills of the testers to eliminate contamination and/or losses and provide the sensitivity needed to demonstrate compliance. After extensive investigation, both internally and with the help of another contractor, our client eliminated any obvious potential causes and was unable to pinpoint what the actual root cause of failure was. The client had to pause normal operations.


The Montrose team was brought in to help determine what could be causing the issue and create a solution. The difference between pass and fail is a minuscule amount which leaves little room for error in these tests. Prior to Montrose becoming involved, the most obvious and common causes had been investigated and ruled out with no indication of causing these issues. On top of normal challenges, this instance was further complicated with less than ideal sampling locations, abnormal sample port locations and exhaust system irregularities, high exhaust gas velocity and temperatures, positive pressures, large dimensions, and limited access for sampling from permanent platforms.


Due to the many abnormal complications with the sample locations, it was suspected that potential contamination was occurring and contributing to the failures to demonstrate compliance.  The Montrose team worked with the project participants and did an in-depth analysis of prior testing details which pointed out the room for contamination in the samples. Though a root cause had not previously been determined, our team suspected that — due to the size of the sampling ducts, the sampling probes, the gas velocity, and the potential for baffles to impart particulate matter into the exhaust stream — loose PM was being mixed in with the analysis collection. Once this was discovered, we took measures to minimize potential sources of contamination as much as possible. In a collaborative effort of experts from many departments at Montrose, we identified and implemented the following best practices: Rigid-ized probes, probe insertion alignment guides, unbreakable and inert probe liners, custom nozzle guards, extended sample durations and higher sample rates. Thanks to this, the regulatory agency accepted the results and all units are now operating normally, without restriction.

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