To Test or Not To Test

My career in the environmental field spans 18+ years and has mainly been focused on all aspects of air quality (emissions testing, regulatory compliance, permitting, reporting, etc.). Throughout my career, one thing has remained constant: each role I’ve held has involved me supporting a variety of industries across broad geographies where regulatory requirements differed immensely. That experience combined with a few recent developments where clients have found themselves in some less than ideal situations involving stack tests, have played a part in writing this article.

As most of you are probably aware, there are a large number of factors that influence the frequency at which you must conduct emissions testing, including industry type, source status (major/minor), and underlying regulations (NSPS/MACT). Further, testing frequency can vary based on the location (State/County) of the facility or even the permit writer.

Emissions testing requirements can range from as frequently as semi-annually to once every five years. Emissions testing may also only be required upon initial start-up or may not even be required at all.

You may think that the less frequent the requirement, the better, but that isn’t always the case.

For example, say your facility is obligated to conduct a performance test under a MACT, and the applicable subpart only requires testing once every five years.  Your facility conducts the initial MACT compliance demonstration and sets the associated operating parameters based on the compliance test. The facility continues to operate according to those set points for the next four and a half years.

The facility environmental and production personnel have confidence in the process/control device, so you schedule and conduct the subsequent 5-year compliance test. Once the results come back, you realize the unit failed the test. Now the agency is calling and wants to know when the unit became non-compliant, and all you have are two sets of data: a recent failed test and a 5-year old passing test.

That’s an unenvious position to find yourself in and a very hard question to answer. It becomes an even harder question to answer the longer the period is between test events.

From a testing standpoint, what could the facility have done to mitigate this situation?

Well, the test in question could have been conducted on a more frequent basis, regardless of what the permit/regulation requires. Many times, and for a variety of reasons, facilities conduct additional non-mandatory testing known commonly as “engineering testing.”

Below are some pros and cons of engineering testing:


  • Limits the length of any non-compliance period directly associated with a failed stack test.
  • Potentially lowers operating costs by reducing the quantity of control device consumables (scrubber additive, ammonia injection, etc.).
  • Provides more accurate/representative data that can be used for a variety of tasks such as: emissions inventory reporting, air modelling, semi-annual monitoring reports, etc.


  • Additional cost
  • Difficulties with scheduling/logistics or production rates
  • Possibility of a failed engineering test

So, the question is: should you conduct additional “engineering testing?”

The answer to this question will be dependent on each of your individual situations and risk tolerance. If your facility’s permit requires annual testing events for all major emission points, then you may decide that there’s no need to conduct additional testing. You may be constrained by cost and be comfortable enough with your process that additional testing would only be an unnecessary expenditure.

The example I provided may seem unlikely and maybe your facility hasn’t experienced a failed stack test, but in my opinion, knowledge is power and there can be many other benefits to conducting additional testing:

  • More frequent test results can further demonstrate on-going compliance
  • Additional data points would allow you to have a more robust compliance program and more knowledge on operating parameters that affect your emission rates
  • The facility could report more representative annual emissions, especially if you’re relying on old/outdated emissions data
  • The facility may even save money as compared to failed/repeat stack tests and possible fines associated with a notice of violation

Not to mention, if your facility fails a compliance test, you will have an increased level of scrutiny and will likely receive more surprise visits by state regulators and maybe even the EPA.

In the end, the decision is up to each facility. If you decide to conduct additional non-mandatory emissions testing (engineering testing), you should do so only after weighing possible outcomes and their associated impacts. I also suggest collaborating with your consultant and/or your internal/external legal counsel prior to moving forward with engineering testing. As with any stack testing event, planning is the most important step.

If you have any questions about this topic or other industrial compliance matters, please feel free to contact the following PPM personnel. We would all be happy to answer your questions.

Alabama: Isaac Smith, Ned Coleman, and Paul Hansen

Louisiana: Karen Brignac, Corey Gautreaux, and Rick Plummer

Mississippi: Annie McIlwain


Contributed by Isaac Smith, District Manager