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Solid Fuel-Fired Heating Device Visible Emission and Opacity Limits

Visible Emission and Opacity Limits are set out in 18 AAC 50.075 and FNSB PM2.5 SIP Section 7.12 (PDF)

Area Opacity Limit During PM2.5 Advisories / Episodes Called by DEC or a Local Air Program Opacity Limit Year Round
FNSB PM2.5 Nonattainment Area Map (PDF)

During PM2.5 Episodes: Solid fuel-fired heating devices may not operate without a waiver from the Department or local air quality program.

During PM2.5 Advisories: Visible emissions may not exceed 20% opacity (for more than six minutes in any one hour, except during the first 15 minutes after the initial startup when the opacity must be less than 50%)

No Black Smoke
State Wide

During PM2.5 Advisories: Visible emissions may not exceed 20% opacity (except for six minutes each hour or 15 minutes after startup)

No Black Smoke

Visible Emission Evaluation Procedures

Opacity Information


(Images above provided by Alaska Environmental Resources, LLC.)

What are Visible Emissions?

  • Emissions you can see
  • Smoke
  • Steam, particulate matter, and gases

What is Smoke Opacity?

  • Opacity is a measure of how much light visible emissions block.
  • High opacity means dirtier smoke is coming out of the chimney.
  • High opacity smoke is a signal that your heating appliance is not operating efficiently and is producing too much pollution.
  • There are easy steps you can take to burn more efficiently, reduce opacity, and produce less pollution.
simulated opacities

What factors affect opacity?

  • Combustion efficiency
  • Operating temperature
  • Wood moisture content
  • Airflow
  • Size of the fire
  • Type of appliance
  • Age and condition of the appliance
  • Types of fuels burned

How can I reduce smoke opacity?

  • Burn dry wood
  • Only burn clean fuels
  • Mix wetter wood with cleaner burning compressed wood logs
  • Increase airflow by opening the damper
  • Build small, hot fires
  • Don't let your fire smolder
  • Maintain your appliance
  • Inspect your stove and make any necessary repairs
  • Consider upgrading to a newer appliance
  • Consider using less polluting heaters that use pellets, propane, oil, or electricity instead

Staff Contact:

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