Revised Air Quality

Emergency Episode Plan 

for the District of Columbia

March 2014

Prepared by:

Monitoring and Assessment Branch

Air Quality Division

District Department of the Environment

1200 First Street NE, Fifth Floor

Washington, DC 20002
TABLE OF CONTENTS

1.0 Classification ...................................................................................................................... 1

2.0 Significant Harm Levels.................................................................................................... 1

3.0 Contingency Plan ............................................................................................................... 2

3.1 Internal Episode Watch .................................................................................................... 2

3.1.1 AIRNow......................................................................................................................... 2

3.1.2 Clean Air Partners........................................................................................................ 3

3.2 Alert.................................................................................................................................. 3

3.3 Warning............................................................................................................................ 3

3.4 Emergency........................................................................................................................ 4

3.5 Termination of an Event................................................................................................... 4

4.0 Emission Reduction Plans................................................................................................. 4

4.1 Alert Level........................................................................................................................ 5

4.2 Warning and Emergency Levels...................................................................................... 5

5.0 Episode Communications.................................................................................................. 5
Emergency Episode Plan

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This Emergency Episode Plan for the District of Columbia (District) is designed to meet the 

requirements of Subpart H of 40 C.F.R. Part 51 (Prevention of Air Pollution Emergency 

Episodes). Its purpose is to establish criteria for determination of the existence of an emergency 

episode. It is also designed to prevent the excessive buildup of air pollutants during air pollution 

episodes, thereby preventing the occurrence of an emergency due to the effects of these 

pollutants on the health of persons. This plan is intended to replace the previous state-adopted 

Emergency Episode Plan from 1976 and is being submitted to the U.S. Environmental Protection 

Agency (EPA) for approval into the District’s State Implementation Plan (SIP).

1.0 CLASSIFICATION

EPA requires emergency episode plans for Priority I areas. The District is a Priority I region for 

particulate matter (PM10), sulfur oxides (SOx), carbon monoxide (CO), and ozone (O3), as

indicated at 40 C.F.R. § 52.471:

Figure 1. Priority Designations per NAAQS Pollutant

Air Quality

Control Region

Particulate 

matter

Sulfur 

oxides

Nitrogen 

dioxide

Carbon 

monoxide Ozone

National Capital Interstate I I III I I

This is because, at one point in time, ambient concentrations of these pollutants in the District 

were greater than the concentrations at 40 C.F.R. § 51.150(b), as included in the following chart:

Figure 2. Concentration Levels to be Classified as a Priority I Region

Pollutant Level Averaging Time

Sulfur dioxide 100 μg/m3

(0.04 ppm) Annual arithmetic mean

455 μg/m3(0.17 ppm) 24-hour maximum

Particulate matter 95 μg/m3 Annual geometric mean

325 μg/m324-hour maximum

Carbon monoxide

55 mg/m3(48 ppm) 1-hour maximum

14 mg/m3(12 ppm) 8-hour maximum

Ozone 195 μg/m3(0.10 ppm) 1-hour maximum

Nitrogen dioxide 100 μg/m3(0.06 ppm) Annual arithmetic mean

Therefore, the District is required to have an Emergency Episode Plan for SOx (represented as 

sulfur dioxide or SO2), PM, CO, and O3. This plan addresses all four pollutants.

2.0 SIGNIFICANT HARM LEVELS

Each plan for a Priority I region includes a contingency plan that, at a minimum, provides for 

taking action necessary to prevent ambient pollutant concentrations at any location in such 

region from reaching the “significant harm levels” at 40 C.F.R. § 51.151, which are also 

provided in Figure 3:
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Figure 3. Significant Harm Levels

Pollutant Level Averaging Time

Sulfur dioxide 2,620 μg/m3(1.0 ppm) 24-hour average

Particulate matter 600 μg/m324-hour average

Carbon monoxide

144 μg/m3(125 ppm) 1-hour

86.3 μg/m3(75 ppm) 4-hour average

57.5 μg/m3(50 ppm) 8-hour average

Ozone 1,200 ug/m3(0.6 ppm) 2-hour average

3.0 CONTINGENCY PLAN

Announcement of the initiation and termination of an episode stage will be made by the Mayor. 

Conditions justifying the proclamation of an internal episode watch, alert, warning, or 

emergency will be deemed to exist whenever the Mayor determines that the accumulation of air 

contaminants in any place is attaining or has attained levels that could, if such levels are 

sustained or exceeded, lead to a threat to the health of the public. Any episode stage may be 

declared on the basis of deteriorating air quality if the Mayor determines that action is required. 

Pollutant concentration will in all cases be measured by EPA-approved methods.

3.1 Internal Episode Watch

The declaration of an Internal Episode Watch will be activated when there is a National Weather 

Service advisory that an Atmospheric Stagnation Advisory is in effect or there is an equivalent 

local forecast of stagnant atmospheric condition. The District relies on AIRNow and Clean Air 

Partners to acquire frequent forecasts of air quality conditions.

3.1.1 AIRNow

EPA calculates an Air Quality Index (AQI) for five major air pollutants regulated by the Clean 

Air Act: sulfur dioxide (SO2), PM, CO, O3, and nitrogen dioxide (NO2). EPA along with the 

National Oceanic and Atmospheric Administration (NOAA), the National Park Service (NPS), 

and tribal, state, and local agencies developed the AIRNow website to provide the public with 

easy access to national air quality information. The website offers daily AQI forecasts and realtime AQI conditions for over 300 cities across the U.S. including the District.

According to the AIRNow website, “the air quality data used in these maps and to generate 

forecasts are collected using either federal reference or equivalent monitoring techniques or 

techniques approved by the state, local or tribal monitoring agencies. Since the information 

needed to make maps must be as ‘real-time’ as possible, the data are displayed as soon as 

practical after the end of each hour. Although some preliminary data quality assessments are 

performed, the data as such are not fully verified and validated through the quality assurance 

procedures that monitoring organizations use to officially submit and certify data on the EPA Air 

Quality System (AQS). Therefore, data are used on the AIRNow Web site only for the purpose 

of reporting the AQI. Information on the AIRNow web site is not used to formulate or support 
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regulation, guidance or any other Agency decision or position.”1 The AIRNow website also 

posts information on “action days” when the AQI gets into the unhealthy range.2 

3.1.2 Clean Air Partners 

In addition, a regional organization called Clean Air Partners issues daily air quality forecasts 

that can be received by email or mobile device for the Metropolitan Washington region. Air 

quality forecasts for this “Enviroflash” service are provided by the Metropolitan Washington 

Council of Governments (MWCOG), Maryland Department of the Environment, Virginia 

Department of Environmental Quality, and District Department of the Environment. Clean Air 

Partners also issues AirAlerts when the Air Quality Index reaches Code Orange or Code Red 

based on real-time monitoring data collected by states in the region and the District. Clean Air 

Partners is chartered by the MWCOG.

3.2 Alert

An alert status will be declared when any one of the following pollutant concentrations is 

exceeded at any monitoring site, as indicated in Appendix L § 1.1(b) of 40 C.F.R. Part 51 and in 

Figure 4:

Figure 4. Alert Status Concentration Levels

Pollutant Level Averaging Time

Sulfur dioxide 800 μg/m3(0.30 ppm) 24-hour average

Particulate matter 350 μg/m324-hour average 

Carbon monoxide 17 μg/m3(15 ppm) 8-hr average

Ozone 400 μg/m3(0.2 ppm) 1-hour average

In addition, adverse meteorological conditions would be such that pollutant concentrations can 

be expected to remain at the above levels or higher for the next twelve hours or more or, in the 

case of ozone, the situation is likely to occur within the next 24 hours unless control actions are 

taken.

According to 40 C.F.R. Part 58 (64 Fed. Reg. 42530, August 4, 1999), the Air Quality Index

Rule, these levels correspond to an AQI value of over 201 to 300, which indicates Code Purple.

3.3 Warning

A warning will be declared when air quality is continuing to degrade and additional control 

actions are necessary and when any one of the following levels is exceeded at any monitoring 

site, as indicated in Appendix L § 1.1(c) of 40 C.F.R. Part 51 and in Figure 5:

 

1

http://www.airnow.gov/index.cfm?action=topics.about_airnow

2

http://www.airnow.gov/index.cfm?action=airnow.actiondays
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Figure 5. Warning Status Concentration Levels

Pollutant Level Averaging Time

Sulfur dioxide 1,600 μg/m3(0.6 ppm) 24-hour average

Particulate matter 420 μg/m3

24-hour average (PM10)

250 μg/m3*24-hour average (PM2.5)

Carbon monoxide 34 μg/m3(30 ppm) 8-hr average

Ozone 800 μg/m3(0.4 ppm) 1-hour average

In addition, adverse meteorological conditions would be such that pollutant concentrations can 

be expected to remain at the above levels or higher for the next twelve hours or more or, in the 

case of ozone, the situation is likely to occur within the next 24 hours unless control actions are 

taken.

These levels correspond to an AQI value of over 300, which indicates Code Maroon.

3.4 Emergency

The emergency level indicates that air quality is continuing to degrade toward a level of 

significant harm to the health of persons and that the most stringent control actions are necessary. 

An emergency will be declared when any of one of the following levels is exceeded at any 

monitoring site, as indicated in Appendix L § 1.1(d) of 40 C.F.R. Part 51 and in Figure 6:

Figure 6. Emergency Status Concentration Levels

Pollutant Level Averaging Time

Sulfur dioxide 2,100 μg/m3(0.8 ppm) 24-hour average

Particulate matter 500 μg/m324-hour average 

Carbon monoxide 46 μg/m3(40 ppm) 8-hr average

Ozone 1,000 μg/m3(0.5 ppm) 1-hour average

In addition, adverse meteorological conditions would be such that pollutant concentrations can 

be expected to remain at the above levels or higher for the next twelve hours or more or, in the 

case of ozone, the situation is likely to occur within the next 24 hours unless control actions are 

taken.

These levels correspond to an AQI value of over 400, which also indicates Code Maroon.

3.5 Termination of an Event

Once declared, any status reached by application of these criteria will remain in effect until the 

criteria for that level are no longer met. At such time, the next lower status will be assumed.

4.0 EMISSION REDUCTION PLANS

Section 6 of the District of Columbia Air Pollution Control Act of 1984 (D.C. Official Code §§ 

8-101 et seq. (2013 Repl.)) and the District Department of the Environment Establishment Act of 

2005 (D.C. Official Code §§ 8-151.01 et seq. (2013 Repl.)) provide the statutory authority to 
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implement 20 DCMR Chapter 4 (Ambient Monitoring, Emergency Procedures, Chemical 

Accident Prevention and Conformity), Section 401 (Emergency Procedures). Section 401 

provides the Mayor with authority to restrain any source from causing or contributing to 

emissions that present an imminent and substantial endangerment to public health, welfare, or 

the environment or to take other action as may be necessary. 

4.1 Alert Level 

In the AQI, Code Purple indicates that air quality is “very unhealthy.” The level triggers a health 

alert signifying that everyone in the affected population may experience more serious health 

effects. Action steps are publicly encouraged, such as:

For sensitive groups – Avoid all physical activity outdoors. Move activities indoors or 

reschedule to a time when air quality is better.

Everyone else – Avoid prolonged or heavy exertion. Consider moving activities indoors 

or rescheduling to a time when air quality is better.

Don’t drive alone. Carpool, take public transit. Telework.

Refuel cars in the evening.

Put off lawn care until air quality improves. Avoid lawn mowing or use an electric 

mower. Don’t use lawn or garden chemicals.

Use a gas or electric grill instead of charcoal.

Turn off lights and electronics when not in use.

Avoid physical outdoor activity.

4.2 Warning and Emergency Levels

In the AQI, Code Maroon indicates that air quality is “hazardous.” The level triggers a health 

warning of emergency conditions where the entire population is more likely to be affected. 

Everyone – Avoid physical activity outdoors.

Sensitive groups – Remain indoors and keep activity levels low.

The following voluntary abatement strategies may be recommended to reduce excessive 

emissions:

Persons operating fuel-burning equipment that requires boiler lancing or soot blowing 

should perform such operations only between the hours of 12 noon and 4 pm.

Persons operating motor vehicles should reduce operations by the use of carpools and 

increased use of public transportation and elimination of unnecessary operation.

When the Director declares an emergency air pollution episode, any person responsible for the 

operation of a source of air pollutants as set forth in Tables 4, 5, and 6 will take actions as 

required for such source and will put into effect a pre-planned abatement strategy for the 

appropriate emergency episode level.

5.0 EPISODE COMMUNICATIONS

In the unlikely event that there would be a smog emergency in the District, staff will seek the aid 

of DDOE’s Chief of Emergency Operations. Actions would take place based on the District’s 
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Response Plan (December 2008, as amended), which is intended to be a living document that 

outlines policies and procedures that reflect the U.S. Department of Homeland Security’s 

(USDHS’s) National Response Framework (NRF). The ultimate goal of the District’s Response 

Plan is to “protect the public and respond efficiently and effectively to significant incidents that 

threaten life, property, public safety, economy, and the environment in the District of Columbia.” 

Other response plan(s) may be referenced as appropriate.