Enforcement and Inspection

What You Should Know About Claiming Affirmative Defense


In general legal terms, an affirmative defense is an admission by a defendant that a crime or a violation has been committed, but that the circumstances were such that the action was necessary or beyond the defendant’s control and thus some level of liability is negated. An example is injuring a person in self defense. While the defendant admits to inflicting the injury, a successfully pleaded affirmative defense would mitigate or remove any subsequent sentence or penalty.

Start-up, Shutdown, and Malfunction

In Sierra Club v. EPA, the D.C. Circuit vacated language the EPA inserted into the NESHAP general provisions that exempted sources from compliance with air emissions standards during periods of start-up, shutdown, and malfunction (SSM). According to the court, in the Clean Air Act (CAA), Congress gave no indication that it intended the application of NESHAP standards to vary based on different time periods. The EPA interpreted the ruling to mean that emissions standards must “limit the quantity, rate, or concentration of emissions of air pollutants on a continuous basis.”


Forget expensive calls to lawyers and consultants. With Enviro.BLR.com, you get instant access, 24/7. Try it out today and get the 2011-2012 EHS Salary Guide, absolutely free. Download Your Free Report.


In its subsequent rulemaking, the EPA asserted that periods of start-up, normal operations, and shutdown are all predictable and routine aspects of a source’s operations and, therefore, continuous compliance during these periods is required. By contrast, the Agency defined “malfunction” as a “sudden, infrequent, and not reasonably preventable failure of air pollution control and monitoring equipment or a process to operate a normal or usual manner.”

Accordingly, the Agency has begun amending NESHAPs by allowing sources to assert an affirmative defense to civil penalties for exceedances of emissions caused by malfunctions. The EPA has not made the affirmative defense available against injunctive relief (i.e., orders to the malfunctioning source to undertake certain actions, such as updating existing control technology).

Substantive Proof

In developing the affirmative defense provision, the EPA asserted that a source would need to present substantial proof to validate that a legitimate malfunction beyond the source’s control had occurred and that the source is not simply disguising a preventable emissions exceedance by claiming it was a malfunction. Therefore, the Agency developed a requirement that an affirmative defense must prove by a preponderance of evidence that the excess emissions:

  • Were caused by a sudden, infrequent, and unavoidable failure of air pollution control and monitoring equipment, process equipment, or a process to operate in a normal or usual manner.
  • Could not have been prevented through careful planning, proper design, or better operation and maintenance practices.
  • Did not stem from any activity or event that could have been foreseen and avoided or planned for.
  • Were not part of a recurring pattern indicative of inadequate design, operation, or maintenance.
  • The source must also demonstrate that:
  • Repairs were made as expeditiously as possible when the applicable emissions limitations were being exceeded and that off-shift and overtime labor were used to the extent practicable to make these repairs.
  • The frequency, amount, and duration of the excess emissions (including any bypass) were minimized to the maximum extent practicable during periods of such emissions.

Need an answer fast? Relax. Our editors guarantee a personalized response to your questions within 3 business days. Take a free trial of Enviro.BLR.com and see what everyone is talking about. For a limited time, also receive the new free special report: 2011-2012 EHS Salary Guide. Download Your Free Report


  • If the excess emissions resulted from a bypass of control equipment or a process, the bypass was unavoidable to prevent loss of life, personal injury, or severe property damage.
  • All possible steps were taken to minimize the impact of the excess emissions on ambient air quality, the environment, and human health.
  • All emissions monitoring and control systems were kept in operation, if at all possible, consistent with safety and good air pollution control practices.
  • All actions in response to the excess emissions were documented by properly signed, contemporaneous operating logs.
  • At all times, the affected source was operated in a manner consistent with good practices for minimizing emissions.

The source must also prepare a root cause analysis to determine, correct, and eliminate the primary cause of the malfunction and notify the EPA as soon as possible but no later than 2 days after the occurrence of a malfunction that caused an exceedance of an emissions limit.