A large, blue, stationary emergency generator lines the right wall of a small engine room.

Understanding Air Quality Requirements for Emergency Generators

Understanding Air Quality Requirements for Emergency Generators

March 17, 2023
Jasmine Sodemann
A large, blue, stationary emergency generator lines the right wall of a small engine room.
Air quality compliance for emission sources, such as boilers and emergency generators, is enforced by federal, state, and local regulatory agencies.

Imagine beginning your day by opening an email from a regulatory agency with the subject line, “Notice of Violation.” No one wants to see a message like this in their inbox.

However, each day a facility operates a stationary engine without understanding the air quality requirements, it risks receiving a notice of violation, a letter of non-compliance, or monetary fines from regulatory agencies. It also risks possible project delays and other costs.

What Is Air Quality Compliance?

The Clean Air Act (CAA) requires the U.S. Environmental Protection Agency (EPA) to establish national ambient air quality standards for certain common and widespread pollutants based on the latest science to protect public health nationwide. Accordingly, the EPA set air quality standards for six common criteria air pollutants:

  • Particulate matter.
  • Ozone.
  • Sulfur dioxide.
  • Nitrogen dioxide.
  • Carbon monoxide.
  • Lead.

All states must adopt enforceable plans to achieve and maintain air quality, meet air quality standards, and control emissions that cross state lines and impact air quality in downwind states. The law calls for new stationary sources, such as power and manufacturing plants, to use the best available technology.

What Are Air Quality Compliance Requirements?

Sections 108 and 109 of the CAA govern developing, reviewing, and revising the National Ambient Air Quality Standards (NAAQS) as appropriate for the six common criteria air pollutants. The CAA requires periodic review of the science on which the standards are based, as well as the standards themselves, to protect the nation’s public health and environment.

Why Do Air Quality Requirements Exist for Emergency Generators?

Stationary internal combustion engines can significantly impact air quality and public health. Emissions from stationary engines include formaldehyde, acrolein, acetaldehyde, and methanol.

Exposure to these toxins may produce various health difficulties for the public. When fuel is burned, engines also emit criteria air pollutants, including:

  • Carbon monoxide (CO).
  • Nitrogen oxides (NOx).
  • Volatile organic compounds (VOCs).
  • Particulate matter (PM).

The health effects of these pollutants include a range of respiratory issues for surrounding communities.

Why Are There So Many Different Rules for the Same Type of Equipment?

No general approach to air regulatory compliance applies to all engines. You can, however, learn all you need to know about the requirements that apply to your stationary emergency engine or one you are considering purchasing. This knowledge empowers you to plan early in your projects, make better decisions in selecting equipment, and avoid regulatory impacts that can delay project schedules, increase costs, and affect your company’s reputation.

The EPA’s air quality requirements for stationary engines differ according to whether the engine is new or existing, is located at an area source or major source of air emissions, and has a compression ignition or a spark ignition. They also differ according to the size of the engine.

The reciprocating internal combustion engine (RICE) rules form the complex basis of federal requirements with which these engines must comply. RICE rules cover the following engines:

  • Engines that burn fuel, not including electric engines or turbines that operate on a different technology than reciprocating engines.
  • Stationary engines, not including mobile sources, such as motor vehicles or lawnmowers, tractors, and forklifts.
  • Portable engines, which may become stationary if they stay in one location for a specific time.

Understanding the Stationary Engine Rules

Several regulations have expanded the number and type of stationary RICE rules that must comply with federal requirements. These include:

  • National Emission Standards for Hazardous Air Pollutants (NESHAP) for RICE to reduce the more toxic compound emissions listed as hazardous air pollutants (HAPS); this is the “RICE NESHAP Rule.”
  • New Source Performance Standards (NSPS) — Standards of Performance for Stationary Spark Ignition Internal Combustion Engines for gaseous fuels; this is the “Spark Ignition NSPS Rule.”
  • Standards of Performance for Stationary Compression Ignition Internal Combustion Engines, the “Compression Ignition NSPS Rule” is for liquid fuels such as diesel or #2 fuel oil.

The intent is to require the manufacturing and operation of new equipment to meet more stringent emission standards using the best available technology.

Most environmental agencies have RICE criteria that exempt smaller engines from air permitting. However, simply because the equipment is small enough not to require permitting, the RICE rules, as well as other local and state rules, may still apply.

Most engines must follow typical minimum requirements, including installing an hour meter and logging operation hours. Older engines have prescribed requirements at specific frequencies for maintenance, including changing the oil and filter, inspecting the air cleaner or spark plugs, and inspecting hoses and belts. Operators must follow the manufacturer’s recommendations for the maintenance of newer engines.

There are typical requirements as described, but there is no one general approach or rule of thumb. For air regulatory compliance, there are many variables to consider. Many factors can affect what requirements apply. For instance:

  • An institutional facility with an engine model year before 2005 may be relieved of any RICE requirements.
  • Two engines with the same power rating but built at different times, say 2004 and 2009, will have entirely different requirements.
  • Joining a demand response program may change an engine’s purpose from emergency use to non-emergency use, thus triggering the need for add-on control devices to meet differing emission standards.
  • Purchasing a brand-new, non-certified engine may lead to high-cost stack testing efforts.

Be sure to visit part II of this discussion, 4 Steps to Managing Emergency Generators for EPA Engine Compliance, in which I provide a four-step process to evaluate your engine and initiate compliance with the requirements.

A portrait of blonde, smiling, Caucasian woman in a black business suit.
Jasmine Sodemann
Vice President, Environmental Compliance & Remediation

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