Focus On Air

Smoke and Air Quality

This information is provided by the Nebraska Department of Environment and Energy to assist the public and regulated community.

Smoke and its Impact on Health
The smoke created by fires can present public health concerns. Smoke contains air pollutants that can be harmful when inhaled, and can be transported long distances, covering large areas of the continent before dissipating. Smoke transport is dependent on numerous factors such as temperature, humidity, and wind conditions.

The pollutant most often associated with smoke impacts is fine particulate matter, or PM2.5. These particles have a diameter of 2.5 microns or less – smaller than that of a human hair – and can be inhaled deeply into the lungs.

National Ambient Air Quality Standards (NAAQS)
The Environmental Protection Agency (EPA) has established health-based (primary) NAAQS for PM2.5 as noted below:

Daily (24-hour) NAAQS
35 ug/m3 (based on a 24-hour average)
Annual NAAQS
12 ug/m3 (based on a year-long average)
(ug = Micrograms)

Compliance with these standards is evaluated by analyzing air monitoring data over a three-year period. For annual NAAQS, a simple three-year average is used; for the daily 24-hour NAAQS, a more complicated calculation is used (i.e., the three-year average of the 98th percentile values, where the 98th percentile value is the annual 8th highest value when monitoring daily).

Nebraska has six ambient air monitors that measure PM2.5 concentrations in or near areas of the highest predicted concentrations (Omaha, Bellevue, Lincoln, Beatrice, Grand Island, and Scottsbluff). Data from these monitors indicate that Nebraska complies with the NAAQS, but also that there are instances when daily PM2.5 concentrations exceed the NAAQS. (The daily PM2.5 NAAQS allows for 7 exceedances per year as described above i.e., the 24-hour average uses the 8th highest value.)

Air Quality Index (AQI)
EPA has developed the AQI to provide the public a simple matrix for real-time air quality conditions. Think of the AQI as a yardstick, ranging from 0 to 500 – the higher the AQI, the greater the level of air pollution and health concern. AQI levels and recommended actions are shown in the following table.

Air Quality Index
Who Needs to be Concerned?
What Should I Do?
It’s a great day to be active outside.

Some people who may be unusually sensitive to particle pollution.
Unusually sensitive people: Consider reducing prolonged or heavy exertion. Watch for symptoms such as coughing or shortness of breath. These are signs to take it easier.

Everyone else: It’s a good day to be active outside.
Unhealthy for Sensitive Groups
Sensitive groups include people with heart or lung disease, older adults, children and teenagers.
Sensitive groups: Reduce prolonged or heavy exertion. It’s OK to be active outside, but take more breaks and do less intense activities. Watch for symptoms such as coughing or shortness of breath.

People with asthma should follow their asthma action plans and keep quick relief medicine handy.

If you have heart disease: Symptoms such as palpitations, shortness of breath, or unusual fatigue may indicate a serious problem. If you have any of these, contact your health care provider.
151 to 200
Sensitive groups: Avoid prolonged or heavy exertion. Move activities indoors or reschedule to a time when the air quality is better.

Everyone else: Reduce prolonged or heavy exertion. Take more breaks during all outdoor activities.
Very Unhealthy
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.
Everyone: Avoid all physical activity outdoors.

Sensitive groups: Remain indoors and keep activity levels low. Follow tips for keeping particle levels low indoors.
Source: *

What Does the AQI Level Mean in terms of the PM2.5 Concentration?
The PM2.5 AQI levels (24-hour) correspond to pollutant concentrations as follows:
AQI Category
PM2.5 Concentration Level
less than 12 ug/m³**
12-35 ug/m³ **
Unhealthy for Sensitive
36-55 ug/m³
56-150 ug/m³
Very Unhealthy
151-250 ug/m³
greater than 250 ug/m³
** Values in the ‘Good’ and ‘Moderate’ category correspond to concentrations that are within the 24-hour NAAQS for PM2.5.

Occasionally Nebraska may experience daily exceedances of the NAAQS for PM2.5, but because the 8th highest value is used when determining compliance, past exceedances have not resulted in regulatory violations of the standard. However, when a short-duration exceedance occurs, it can and does have public health impacts as indicated in the AQI table above. The source of the smoke is predominantly from outside Nebraska and the frequency of these episodes has not resulted in violation of the NAAQS, so Nebraska currently has no regulatory recourse to address these exceedances.

How can I evaluate the impact of smoke in the air?

· Check the AQI – current conditions and the forecast are available on EPA’s AirNow website ( For data from Nebraska monitors and sensors, please visit - click on the individual monitor or sensor to open the data window and scroll for data and info. Please note that data from past smoke incidents indicate that the AirNow forecasts lack some accuracy in relating current air quality conditions to the 24-hour average conditions.

· Check local health agency and NDEE webpages and social media for updates.

· Use your senses. Is the air hazy? Does it smell smoky? Elevated concentrations of PM2.5 produce a visible haze that may indicate smoke impact before you smell the odor of smoke.

· Past incidents tend to follow a similar pattern:

· Prescribed burning – smoke tends to accumulate in the late afternoon or evening hours, is most noticeable in the early morning hours, and then dissipates in mid-late morning as temperatures increase.

· Wildfires – smoke may accumulate at any time of the day, and can be persistent and linger, sometimes over a period of days.

· Plan activities accordingly to avoid periods of highest PM2.5 and smoke impacts using the AQI table as a guide.

NDEE is committed to working with other states and sources of smoke to minimize and, if possible, eliminate adverse impacts. Comments, suggestions and questions regarding air quality issues and agency activities are welcomed. For more information, contact NDEE at (402) 471-2186, or toll free at 1-877-253-2603; e-mail –