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Many facilities and businesses in Minnesota — ranging from large hospitals and grocery stores to farms and small businesses — use stationary engines or generators for emergency backup power, routine power generation, and even to help level out demand on the electrical grid. But just like any other fuel-burning engine, they emit pollutants when in use. If your stationary reciprocating internal combustion engine (RICE) has the potential to emit pollutants in excess of certain thresholds, you will need a permit to operate it. Follow our steps to determine if state and federal air regulations apply to you.

NOTE: If your facility already has an air-emissions permit but it doesn't cover your stationary engine, or you are adding a new engine, visit the Facilities with existing air permits page.

First step: Determine your potential to emit

The need for an air permit is based on the volume of emissions a facility or business can produce, which is called your potential to emit (PTE). An engine's PTE is based on its maximum capacity while operating at the maximum hours of operation, so it's typically calculated based on operating 8,760 hours per year.

The MPCA has developed a calculator to help you determine your engine's PTE. If you have more than one stationary engine, the calculator provides space to determine PTE for each one. To use the calculator, you'll need some basic information about your engine(s):

  • Engine make and model
  • Engine output in kilowatts
  • Fuel type — Does your engine run on gasoline, diesel, natural gas, or propane?
  • Maximum-rated fuel usage per hour (natural gas and propane engines)
  • Horsepower (gas and diesel engines)
  • Displacement rate (liters per cylinder)
  • Tier certification (diesel only)
  • Date of manufacture (on engine nameplate)
  • Year the engine was installed at your site
  • Date of most recent engine rebuild
  • Engine used routinely or only during emergencies?
  • Do you have an agreement with your power company on peak shaving or emergency demand response (see information below)?

You may need to locate the manufacturer's specifications sheet in your files or online. When you've gathered the information, open the calculator and follow the instructions. Navigate using the colored tabs along the bottom:

Contact us for assistance in completing the calculator.

Peak shaving and emergency demand response agreements

Facilities with stationary generators may form agreements with their local power utility to help level out demand on the public power grid. Some facilities do "peak shaving" by generating their own power when public demand for power spikes. They may also lower their energy consumption during periods of high power usage — called "emergency demand response" — to better match the demand for power with the supply available from the power utility. You'll need to know if your facility has a peak shaving or emergency demand response arrangement with your local power utility to determine whether you need an air permit.

Facilities with other sources of air pollution

The need for a permit is based on your entire business's potential air emissions. If your business doesn't already have an air permit, you need to assess all your activities that put pollutants into the air to determine what type of permit you might need. Learn more on the Calculating emissions page.

Second step: Check if federal rules apply to you

Do federal air pollution standards apply to your facility? The regulation navigation tools in the table below will help you answer the question.

  National emission standards for hazardous air pollutants (NESHAP) New source performance standards (NSPS) New source performance standards (NSPS)
Regulation 40 CFR 63, subp. ZZZZ 40 CFR 60, subp. IIII 40 CFR 60, subp. JJJJ
Applies to Stationary reciprocating internal combustion engines Standards of performance for compression ignition (diesel) engines Standards of performance for spark ignition (gaseous) engines
Does it apply to you? NESHAP regulation navigation tool NSPS regulation navigation tool (diesel) NSPS regulation navigation tool (gaseous)

Tips for small sources of air emissions

  • The NESHAP rule is for engines constructed prior to June 12, 2006.
  • The NSPS rule is for engines constructed on or after June 12, 2006.

NESHAP and NSPS regulations may also apply to:

  • construction, modification, or reconstruction activities at affected facilities.
  • coating operations, metal fabricators and finishers, and asphalt processors with stationary engines.
  • nonmetallic mineral processors, hospital waste incinerators, and sewage treatment plants.

See the "Federal standards" tab in the calculator for more information.

Third step: Apply for needed permits

After plugging your engine information into the calculator, go to the "Potential emissions" and "Actual emissions" tabs; you may have to scroll to the right of the calculator's engine tabs to see them.

The potential emissions tab shows your facility's potential emissions compared to permitting thresholds, based on the information you entered.

  • You require an air permit if your facility-wide potential emission totals on this tab are greater than the permitting threshold for one or more pollutants
  • You may not require an air permit if your facility-wide potential emission totals are less than the permitting thresholds for all pollutants. The NESHAP or NSPS standards must still be followed, if applicable.

The actual emissions tab shows your actual emissions compared to Registration Option D permit limits, based on the fuel use amounts you entered.

  • You may qualify for an Option C or D permit if your facility-wide actual emissions totals are less than the Option D permit limits for all pollutants, as shown on this tab.

After you've reviewed your potential and actual emissions, click on the "Permits and requirements" tab for more information about permits and links to application materials.


Whether or not you require an air permit to operate your stationary engine(s), you can still take steps to reduce its impact on our air quality: