Under Sections 550-562 of the Rules for the Control of Air Pollution in Idaho (pdf on Department of Administration Web site), known as the Air Pollution Emergency Rule, DEQ is authorized to manage and remedy pollution levels that may constitute a health emergency. The rule is designed to:

• define criteria for an air pollution emergency,
• formulate a plan for preventing or alleviating such an emergency, and
• specify procedures for carrying out the plan.

The Air Pollution Emergency Rule outlines criteria that enable DEQ to take appropriate action when levels of regulated air pollutants cause or are predicted to cause a health emergency. The rule identifies four stages or levels of an emergency, with each stage addressing a progressively more serious air quality event.

Levels of pollutants in the atmosphere are determined through analysis of meteorological and ambient air quality monitoring data gathered by DEQ. Four criteria stages have been established for carbon monoxide (CO), nitrogen dioxide (NO2), ozone (O3), particulate matter with an aerodynamic diameter of 2.5 and 10 micrometers or less (PM2.5 and PM10), and sulfur dioxide (SO2). The criteria apply to any situation or circumstance where pollutants reach, or are predicted to reach and persist, at potentially unhealthful levels. Find out more about the health impacts of air pollution on DEQ's Health and Air Pollution Web page.

Following are the criteria levels for each of the four stages of an air pollution emergency:

Emergency criteria apply to any situation or circumstance where pollutants reach, or are predicted to reach and persist at, potentially unhealthful levels. Once an episode stage is reached or DEQ has determined that reaching a particular stage is imminent, emergency action corresponding to that stage will remain in effect until air quality measurements indicate that another stage (either lower or higher) has been attained. At such time, actions corresponding to the next stage will go into effect. This procedure will continue until the episode is terminated.

The following actions are required during each of the four air pollution emergency stages:

 Stage 1: Air Pollution Forecast and Caution

 Stage 2: Alert

Includes the measure for Stage 1 and:

• Using burners and incinerators to dispose of solid waste is prohibited.
• Operating fuel-burning equipment that requires boiler lancing or soot blowing is limited to between 12 noon and 4 p.m.
• Commercial, industrial, and institutional facilities using coal or residual fuel oil must switch to natural gas or distillate oil if available.

 Stage 3: Warning

Includes all measures for Stages 1 and 2 and:

• Commercial, industrial, and institutional facilities using coal or residual fuel oil must either switch completely to natural gas or distillate oil or, if these low-sulfur fuels are not available, curtail the use of existing fuels to the extent possible without causing injury to persons or damage to equipment.

 Stage 4: Emergency

Includes all measures for Stages 1, 2, and 3 and:

• All places of employment must either stop operations immediately or reduce emissions to the maximum extent possible.
• When an emergency episode is declared for carbon monoxide, driving motor vehicles is prohibited except in emergencies or with the approval of local or state police or DEQ.

It is DEQ's responsibility to inform the public of air pollution emergencies. Via the news media, DEQ takes the following actions during air pollution episodes:

• Defines the extent of the problem
• Indicates actions taken
• Provides the air pollution forecast
• Gives notice when the next update will occur
• Outlines the procedures that must be implemented by the public, commercial, institutional and industrial sectors
• Isues specific warnings and advice to those who because of acute or chronic health problems may be most susceptible to the effects of the episode.