Air Quality Resources


This page provides extra resources relating to fine particulate pollution, burning indoors, burning outdoors, air pollution from wildfires, and health effects of air pollution.  Use the menu above to navigate to the topic you wish to learn more about.

If you have additional questions about air quality, contact our office at 406-447-8351.

Fine Particulate Pollution

Particle pollution (also called particulate matter or PM) is the term for a mixture of solid particles and liquid droplets found in the air. Some particles, such as dust, dirt, soot, and smoke, are large or dark enough to be seen with the naked eye. Others are so small they can only be detected using an electron microscope.

Particle pollution includes "inhalable course particles," with diameters larger than 2.5 micrometers and smaller than 10 micrometers, and "fine particles," with diameters of 2.5 micrometers and smaller.

How small is 2.5 micrometers? Think about a single strand of hair from your head. The average human hair is about 70 micrometers in diameter, making it 30 times larger than the largest fine particle.

These particles come in many sizes and shapes and can be made up of hundreds of different chemicals.

Some, known as "primary particles," are emitted directly from a source, such as construction sites, unpaved roads, fields, smokestacks, or fires.

Others form in complicated reactions in the atmosphere from such chemicals as sulfur dioxides and nitrogen oxides emitted from power plants, industries, and automobiles. These particles, known as "secondary particles," make up most of the fine particle pollution in the country.

study conducted by the University of Montana(PDF, 393KB) during the winter of 2007/2008 found that wood smoke was the major source of fine particulate pollution in the Helena Valley during the winter. It contributed 66 percent of the particulate pollution measured (see chart below). 


Burning Indoors

The use of wood-burning stoves and fireplaces in the Lewis and Clark County Air Pollution Control District is governed by the county outdoor air-quality regulations.(PDF, 185KB)

The health department monitors air quality all year, but winter is when poor air-quality conditions are most likely to occur. This happens when layers of warm air cause inversions that trap smoke, vehicle exhaust, and other pollutants in the Helena Valley.


When air quality is poor, burning is restricted in the Air Pollution Control District to protect the health of area residents. Restrictions are determined by taking an 8-hour average of the concentration of fine-particulate pollution and looking at air-dispersion forecasts provided by the Montana Department of Environmental Quality.

Air Quality Designations

Air Quality Particulate Level Weather Forecast Burning Status
GOOD 0-21 ug/m3 Good air dispersion and favorable weather conditions Wood burning allowed
WATCH 21-28 ug/m3 Good air dispersion predicted for next 24 hours Residents asked to voluntarily stop or reduce burning
POOR 28-35 ug/m3 Poor air dispersion or stagnant air, inversions predicted Only pellet and EPA-certified stoves may be used



The health department enforces burning restrictions by observing emissions from chimneys, noting the address, and mailing out a notice of violation. Violators are subject to criminal fines as follows:

  • 1st violation in a calendar year: Warning
  • 2nd violation: $100 fine
  • 3rd violation: $250 fine
  • Additional violations: $500

How to Burn Your Stove Cleanly

Smoke from wood stoves is the primary source of winter particulate air pollution in Lewis and Clark County. How you burn your wood stove affects how much pollution it produces.

  • Burn only dry, well-seasoned wood. This reduces particulate and carbon monoxide emissions and produces more heat.
  • Start your fire with small, dry kindling to establish a hot flame. Gradually add wood of 4-5 inches in diameter to maintain a hot, clean fire.
  • Keep the damper open enough to maintain a clean, hot fire. Smoldering fires cause 6 times more pollution than hot, clean fires.
  • Don't pack too many logs in your stove. Smaller, hotter fires are more efficient and less polluting.
  • Check for creosote buildup. A clean chimney increases wood-burning efficiency and reduces the chance of dangerous chimney fires.
  • Avoid burning during warm weather. Burning when the outside temperature is above 40 degrees Fahrenheit requires constant dampening, increasing emissions.
  • Go outside and check your chimney for smoke. About 15 minutes after you start your fire, you should see very little smoke coming from the chimney.
  • Check local air quality daily. Be sure to follow health department advisories and restrict burning when warnings are issued.
Why bother?  When you burn a hot, smokeless fire in your wood stove, you:
  • Improve air quality in your home and outdoors;
  • Reduce the creosote that builds up in your chimney and so reduce the fire hazard;
  • Use less wood, saving time and money; and
  • Help to protect your health and that of your family, friends, and neighbors.

For more helpful information, see the EPA's Burn Wise website

Burning Outdoors

If you plan to burn yard waste or slash, you must first get a burn permit. You can pick up a permit at the Lewis and Clark County Clerk and Recorder's Office, Room 113, City-County Building, 316 North Park, Helena.

Outdoor burning is regulated by the Montana Department of Environmental Quality. If you have questions, the department operates a hotline at 1-800-225-6779.

Air Pollution from Wildfires

Corral Fire, June 2012

Wildfire smoke contains dangerous pollutants. These can hurt your eyes, irritate your throat and lungs, and worsen existing heart and lung disease.

The effects of breathing smoke from wildfires vary from person to person. They also depend on how long a person is exposed to the smoke and what pollutants are in it. Some of the short and long-term effects can be:

  • Irritation of eyes and respiratory tract
  • Persistent cough and wheezing
  • Asthma or bronchitis
  • Reduced lung function
  • Aggravation of existing breathing and heart diseases

Most healthy adults recover quickly from smoke exposure. Some people are more sensitive, and they may experience more severe short-term or long-term symptoms.

Sensitive Groups

  • Children
  • The elderly
  • People with asthma or other breathing diseases
  • People with high blood pressure or heart disease
  • Smokers

Pollutants in Wildfire Smoke

The composition of smoke varies depending on the type of fuel. Different woods are made up of different amounts of cellulose, tannins, resins, waxes and other compounds, which produce different pollutants when burned.

The most common ingredients in smoke are carbon dioxide, water vapor, carbon monoxide, fine particulate matter, nitrogen oxides, and hydrocarbons.

Protecting Your Health

Here are some tips for coping with wildfire smoke and reducing its impacts on your health:

  • Pay attention to local air quality reports.
  • Watch for health warnings about smoke and follow recommended safety measures, like limiting or avoiding time outdoors
  • Pay attention to visibility guides. These can help you determine how much pollution is in the air. (See the guide below.)
  • Stay indoors when advised, and keep your indoor air as clean as possible. Keep windows and doors closed. Run an air conditioner if you have one, but keep the fresh-air intake closed and the filter clean to prevent outdoor smoke from getting in. If you don’t have an air conditioner and it’s too warm to stay inside with the windows closed, seek shelter elsewhere.
  • Reduce indoor pollution. When smoke levels are high, don’t use anything that burns. Don’t vacuum, because that stirs up particles already inside your home. Don’t smoke, because that pollutes the air even more.
  • Follow your doctor’s advice if you have asthma or another lung disease. Call your doctor if your symptoms get worse.
  • Don’t rely on dust masks for protection. The paper masks you find at hardware stores are made to trap large particles, like sawdust. They won’t protect your lungs from smoke. An N95 mask, worn properly, will offer some protection.
  • Avoid smoke exposure during outdoor recreation. If smoke conditions become severe, officials may decide to postpone or cancel local activities.
More Information

Recommendations for Outdoor Activities Based on Air Quality for Schools and Child Care Facilities(PDF, 561KB) (Montana Department of Public Health and Human Services) 

Wildfires (American Lung Association)

US Environmental Protection Agency - Wildfires

Health Effects of Air Pollution

boy with asthma inhaler

Smoke may smell good, but it's not good for you. Wood smoke can affect everyone, but children under 18, older adults, people with diabetes, heart disease, asthma or other lung diseases are the most vulnerable. (See "Smoke and Health Effects in Children(PDF, 306KB)")

Smoke is made up of a complex mixture of gases and fine particles produced when wood and other organic matter burn. A major health threat from smoke comes from fine particles (also called particle pollution, particulate matter, or PM). These microscopic particles can get into your eyes and respiratory system, where they can cause health problems such as burning eyes, runny nose, and illnesses such as bronchitis.

How Fine Particles Can Affect Your Health

Particle exposure can lead to a variety of health effects. For example, several studies link particle levels to increased hospital admissions and emergency room visits. It can even lead to death from heart or lung diseases.

Both long- and short-term particle exposures have been linked to health problems. For a more complete discussion of research on the health effects of wood smoke, see the Environmental Protection Agency's publication Health Effects of Breathing Wood Smoke.

Long-term exposures, such as those experienced by people who live for many years in areas with high particle levels, have been associated with problems such as reduced lung function and the development of chronic bronchitis—and even premature death.

Short-term exposures to particles (hours or days) can aggravate lung disease, causing asthma attacks and acute bronchitis. They may also increase susceptibility to respiratory infections.

To learn more about asthma:

Protect Yourself and Others!

Follow the guidelines we have provided on this website for using your wood-burning appliance efficiently and safely. It's important to limit your exposure to smoke—especially if you are more susceptible than others:

  • If you have heart or lung disease, such as congestive heart failure, angina, chronic obstructive pulmonary disease, emphysema, or asthma, you may experience health effects earlier and at lower smoke levels than healthy people.
  • Older adults are more likely to be affected by smoke, possibly because they are more likely to have chronic heart or lung diseases than younger people.
  • Children also are more susceptible to smoke for several reasons: their respiratory systems are still developing; they breathe more air (and air pollution) per pound of body weight than adults; and they're more likely to be active outdoors.