DocumentSmoke and Air Quality 

Smoke from wildfires can have significant impacts on air quality, with resulting health impacts. Summit County Public Health works with the Colorado Department of Public Health to monitor air quality and notify the public about unhealthy conditions.

 This page contains information on:

Health Impacts of Smoke

The size of particles is directly linked to their potential for causing health problems. Small particles less than 2.5 micrometers in diameter pose the greatest problems, because they can get deep into your lungs, and some may even get into your bloodstream.

Exposure to such particles can affect both your lungs and your heart. Numerous scientific studies have linked particle pollution exposure to a variety of problems, including:

  1. Document (1) - CopyPremature death in people with heart or lung disease
  2. Nonfatal heart attacks
  3. Irregular heartbeat
  4. Aggravated asthma
  5. Decreased lung function
  6. Increased respiratory symptoms, such as irritation of the airways, coughing or difficulty breathing.
  7. Image comparing Particulate Matter to a strand of hair Opens in new window
Tools to Assess Air Quality Risk

The U.S. Air Quality Index (AQI) is EPA’s index for reporting air quality. It can be used for assessing air quality related to a variety of pollutants; including ozone, nitrogen oxides and particulate matter (PM).

How does the AQI work?

Think of the AQI as a yardstick that runs from 0 – 500.  The higher the AQI value, the greater the level of air pollution and the greater the health concern. For example, an AQI value of 50 or below represents good air quality, while an AQI value over 300 represents hazardous air quality.

For each pollutant, an AQI value of 100 generally corresponds to a measured ambient air concentration that equals the level of the short-term national ambient air quality standard for protection of public health. AQI values at or below 100 are generally thought of as satisfactory. When AQI values are above 100, air quality is unhealthy; at first for certain sensitive groups of people, then for everyone as AQI values get higher.

The AQI is divided into six categories. Each category corresponds to a different level of health concern. Each category also has a specific color. The color makes it easy for people to quickly determine whether air quality is reaching unhealthy levels in their communities.

People with heart or lung diseases, children, older adults and pregnant women are the most likely to be affected by particle pollution exposure.

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Because an AQI is reported based on the presence of several different pollutants, it is important to consider that an AQI value is issued based on the pollutant that is producing the worst value.  For example, ozone in an area may be high and result is an AQI in the Unhealthy category while the PM2.5 is producing a Good AQI.  The overall AQI reported will be Unhealthy.  In Summit County, an AQI will generally be based on PM2.5 because there are currently no sensors for any of the other pollutants. 

Two (2) primary tools can easily be used by the public to assess the risk of smoke levels in the air:

  • Document (3)Visibility- 
Smoke particles in the air (specifically PM2.5) will impair visibility.  The table below correlates visibility to the AQI.  It also shows values as measured by a sensor (see next tool). When visibility is less than 5 miles, air quality has become unhealthy…first for sensitive groups and then for everyone below 3 miles.  Typical messaging includes a generic reference to air quality being unhealthy when visibility is less than 5 miles.  

  • Sensors-
The particles most harmful to humans are 2.5 micrometers (µm) in size and smaller so the unit of measuring these particles is referred to as PM2.5.  PM2.5 values are reported in micrograms per cubic meter of air (µg/m3). See table above.

PM2.5 risk is most accurately assessed using a mechanical sensor or monitor.  Traditionally monitors cost in the neighborhood of $10,000-25,000 each so there are very few around. They are typically installed in areas that are subject to regulatory exceedance for PM and/or those that have high population density.  Recently, low cost PM2.5 sensors have become available including the PurpleAir .  Summit County has a few Purple Air sensors around the county.  It is important to understand that these low cost sensors are not considered accurate enough to be used in a regulatory action.  However, an independent study found that these sensors have 95-99.5% precision compared with the more expensive reference instrument.  At medium to high concentrations of PM2.5 they are 99.5% precise.

In order to obtain the results from monitors and sensors, visit EPAs page . Page


Sensor Display

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To see a specific sensor go to the Fire and Smoke Map page. Zoom to your desired location and click on the sensor located in the geographic area you are interested in. You will see the following details for that sensor:

It is important to remember that the AQI for PM is calculated using the 24-hour (1-day) average.

Sensors communicate AQI for a variety of time intervals but the default is 24 hours since this is the interval used to generate the AQI.  Hourly and ten minute values may be viewed by selecting from the various time options. Communicating risk in 10-minute average intervals is not in line with the EPA guidance for calculating AQI and therefore the public is advised not to take a short-term value and assign an AQI when that system is set up based on a 24-hour average exposure.  Being exposed to moderate to heavy smoke for a short-term may not have the same health impacts as being exposed to that value for a full 24-hours.

As you evaluate the sensor data it is important to consider the quality of the data being presented. PurpleAir sensors are not always maintained well.  If you see a sensor that is abnormally high compared with other sensors in the vicinity it may need servicing.  Occasionally a large particle or insect may become lodged in the sensor and be resulting in inaccurately high values.  If you see this, report the abnormality to PurpleAir.

Minimizing The Risk Of Unhealthy Smoke

The following actions may be taken to minimize smoke exposure:

  • If you have heart or lung disease, check with your doctor about what you should do during smoke events. Have a plan to manage your condition.
  • Know how you will get alerts and health warnings, including air quality reports, public service announcements (PSAs), and social media warning you about high fire risk or an active fire.  Anyone can sign up to receive such reports from CDPHE
  • Or from the Summit County emergency alert system.
  • Stay indoors if it is smoky – this is the best way to reduce your exposure.
  • Stock up so you don’t have to go out when it’s smoky. Have several days of medications on hand. Buy groceries that do not need to be refrigerated or cooked because cooking can add to indoor air pollution.
  • Ask an air conditioning professional what kind of high efficiency filters to use in your home’s system and how to close the fresh-air intake if your central air system or room air conditioner has one.
  • Document (4)Create a “clean air room” in your home by closing windows / doors and running an air filtering unit such as a portable HEPA filter or a DIY box fan filter system.
  • Have a supply of N95 respirators and learn how to use them. They are sold at many home improvement stores and online. These will not eliminate the exposure but may reduce it.
  • Leave the Area If you are beginning to experience symptoms, consider temporarily locating to another area that has less smoke as long as it is safe for you to do so.
The table below can be used to assist schools, child care centers and even the general public in assessing whether or not to engage in physical activities, especially when those activities are outside.

  • Document (5)Limit Outdoor Activities - Regular physical activity – at least 60 minutes each day – promotes health and fitness. This table shows when and how to modify outdoor physical activity based on the AQI. This guidance can help protect the health of all persons, including children and teenagers, who are more sensitive than adults to air pollution.
*Watch for symptoms. Air pollution can make asthma symptoms worse and trigger attacks. Symptoms of asthma include coughing, wheezing, difficulty breathing, and chest tightness. Even persons who do not have asthma could experience these symptoms.

If symptoms occur: A person might need to take a break from actitivies, do a less intense activity, stop all activity, go indoors, or use quick-relief medicine as prescribed. If symptoms don’t improve, get medical help.

See also:

Information Resources on Smoke and Health

Quick Links

Frequently Asked Questions
If smoke is unhealthy in my area, how do I reduce my risk?

There are a few simple actions you should consider that can minimize exposure to smoke that makes its way into a community.  Steps include relocating, closing doors/windows at night, using an air filter, etc.  For additional tips and details see:

Will a mask eliminate the risks posed by smoke exposure?
A properly sized N95 or P100 mask will help but does not eliminate the unhealthy air quality to healthy levels.
Where are fires burning in the area?
What are the long term effects of low to moderate smoke levels?
According to Denver's National Jewish Health, healthy individuals are at very minimal risk for long-term effects from breathing wildfire smoke. Once exposure to the smoke goes away, so should any symptoms.

Firefighters and other safety personnel are at risk for health concerns due to long-term exposure as they work endlessly to put out wildfires. Smoke inhalation, long working hours and scorching temperatures all contribute to health concerns. Long-term respiratory problems could be seen down the road, such as decreased lung function, although these effects could be reversible. The proper use of personal protective equipment (PPE) is paramount to mitigating the effects of smoke exposure.

For a more thorough list of FAQs see: