What is a Code Orange or Code Red air quality alert?

WASHINGTON, D.C. - When wildfire smoke or ozone pollution pushes air quality into unhealthy territory, officials often issue color-coded alerts. But what does Code Orange mean, and how is it different from Code Red?

What we know:

The U.S. Air Quality Index, or AQI, is the EPA’s system for reporting how clean or polluted outdoor air is and what health effects people should be aware of. The higher the AQI number, the greater the level of pollution and health concern.

The AQI is divided into six color-coded categories: Green, Yellow, Orange, Red, Purple and Maroon. Green is the cleanest category, while Maroon is considered hazardous.

Code Orange and Code Red are two of the most common alerts people see during wildfire smoke, ozone or fine particle pollution events.

What does Code Orange mean?

Code Orange means the air is "unhealthy for sensitive groups."

That category covers AQI values from 101 to 150. At that level, members of sensitive groups may experience health effects, while the general public is less likely to be affected.

Sensitive groups can include:

• Children
• Older adults
• People with asthma
• People with heart disease
• People with lung disease
• People who are active outdoors
• People who work outside

During a Code Orange alert, sensitive groups should reduce prolonged or heavy outdoor exertion. AirNow says that for particle pollution, sensitive groups include people with heart or lung disease, older adults and children.

The D.C. region is under a Code Orange Air Quality Alert for Thursday, July 16. The alert covered the District of Columbia, suburban Maryland and Northern Virginia, with officials warning that pollution levels could become unhealthy for sensitive groups.

What does Code Red mean?

Code Red means the air is "unhealthy."

That category covers AQI values from 151 to 200. At that level, some members of the general public may experience health effects, while sensitive groups may experience more serious health effects.

During a Code Red alert, everyone should reduce exposure to air pollution. Sensitive groups should be especially careful and avoid prolonged or heavy outdoor exertion.

Pennsylvania was under a statewide Code Red Air Quality Action Day on Thursday because of wildfire smoke from Canada and Minnesota. The alert was issued for fine particle pollution, also known as PM2.5.

RELATED: Code Red air quality alert in effect across Pennsylvania due to Canadian wildfire smoke

Code Orange vs. Code Red

The main difference is who is at risk.

Code Orange is mainly a warning for sensitive groups. Code Red is a warning for everyone.

On Code Orange days, many healthy adults may not feel symptoms, but people with asthma, COPD, heart disease or other risk factors may have trouble breathing, chest tightness, coughing or worsening symptoms.

On Code Red days, the air is unhealthy enough that even people without known health conditions may feel the effects, especially if they are exercising, working outside or spending long periods outdoors.

Why wildfire smoke affects air quality

Wildfire smoke can carry fine particle pollution, also called PM2.5.

Those particles are small enough to get deep into the lungs and can make breathing harder, especially for people with asthma, COPD, heart disease and other health conditions.

That is why wildfire smoke can trigger air quality alerts hundreds or even thousands of miles from the fire itself.

What should you do during an air quality alert?

During a Code Orange or Code Red alert, check your local AQI before making outdoor plans.

People in sensitive groups should consider staying indoors, shortening outdoor activity or moving exercise inside. On Code Red days, everyone should limit prolonged or heavy outdoor activity.

Other ways to reduce exposure include:

• Keep windows and doors closed.
• Use air conditioning on recirculate.
• Avoid outdoor workouts.
• Keep car windows closed and use recirculated air.
• Avoid adding more pollution by postponing lawn mowing, grilling or unnecessary driving.
• Follow your asthma or COPD action plan if you have one.
• Contact a health care provider if symptoms get worse or do not go away.

How to check your local air quality

Air quality can vary by neighborhood and change throughout the day.

You can check current conditions through AirNow.gov, local environmental agencies or weather alerts from the National Weather Service.

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