Sources of Indoor Particulate Matter (PM)
Particulate matter (also referred to as PM or particle pollution) is a complex mixture of solid and/or liquid particles suspended in air. These particles can vary in size, shape, and composition.
EPA is especially concerned about tiny particles that are 10 micrometers in diameter or smaller – that’s at least 5 times smaller than the width of a human hair. These particles can be inhaled deeper into the lungs than larger particles, where they can cause serious health effects. Some of the health effects of PM include decreased lung function and aggravated asthma.
PM is found outdoors and in all indoor environments. There are many sources of PM indoors and actions you can take to reduce or control them.
![Image of Indoor Particulate Matter Logo](/https/www.epa.gov/sites/default/files/styles/large/public/2016-02/nas-pm.jpg?itok=hEjrtiD_)
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Did you know?
Chemical reactions can generate PM indoors.
Chemicals in the air, such as those released from peeling an orange or using a cleaning solution, can react together to produce PM.
Where does indoor PM come from?
PM found indoors includes particles that come from outdoor air and particles that are generated indoors.
Outdoor air brings particles indoors when it enters through windows and doors. PM can also enter through small openings and cracks in walls and foundations.
Indoors, PM is generated by:
- cooking,
- some cleaning activities,
- combustion activities,
- burning candles,
- use of fireplaces,
- use of unvented space heaters,
- kerosene heaters, and
- tobacco and other smoking products.
- biological contaminants,
- animals,
- pests,
- plants, and
- mold.
- printers, and
- indoor chemical reactions.
How can I reduce sources of PM indoors?
Usually, the best way to reduce indoor PM is to reduce its sources. Some sources, such as burning candles, may be possible to stop completely. Others, such as cooking and cleaning, can be controlled or reduced. Below you will find more information about sources of indoor PM and actions you can take to reduce or control them.
PM from Outdoor Air Pollution
PM in outdoor air is also known as outdoor particle pollution. PM from outdoor air is an important source of indoor PM. Outdoor and indoor air are constantly mixing together. So, some outdoor air is always coming into your home. When it does, it brings PM with it. Outdoor PM can come in through open doors and windows. It can also come in through small cracks and crevices.
Car exhaust, smoke, road dust, pollen and some factory emissions contain PM. Wildfires are another source of outdoor PM. In addition, PM can be released into the air from burning buildings and any other burning materials. Outdoor PM can be high any time of year. PM is higher near busy roads and where people burn wood.
Actions You Can Take
- Keep your windows closed when outdoor pollutants are high. Check local outdoor air quality on AirNow.gov to know when and where air pollution may be high.
- Keep your windows closed on high pollen days.
- Install higher efficiency filters in your heating, ventilation, and air conditioning (HVAC) system.
- Use portable air cleaners. Learn more about air cleaners and filters.
- Learn more about how to reduce the amount of wildfire smoke that can get into your home. Visit: Wildfires and Indoor Air Quality (IAQ).
- Take action to maintain or improve indoor air quality when weatherizing your home. Weatherization can help reduce the amount of outdoor air, which can include PM, that enters your home. Learn more about weatherization and IAQ.
Additional Resources
- Particulate Matter Pollution
- How Smoke from Fires Can Affect Your Health
- Create a Clean Room to Protect Indoor Air Quality During a Wildfire
- Smoke-Ready Toolbox for Wildfires
- Wildfires
- Environmental Law Institute - Reducing Indoor Exposure to Particle Pollution from Outdoor Sources: Policies and Programs for Improving Air Quality in Homes
Cooking
Many cooking appliances and the process of cooking itself can increase levels of indoor PM. The type of food being cooked, the cooking method (i.e., grilling, frying, baking, or sautéing), and the type of cooking fat used will all impact how much PM is produced when cooking. Burning food during cooking quickly produces large quantities of indoor PM. Improving ventilation and filtration during cooking can reduce exposure to indoor PM.
Actions You Can Take
- If you have a range hood over your stove, use it whenever you are cooking. Using stove range hoods while cooking can greatly reduce indoor PM exposure from cooking.
- Vent the range hood to the outdoors, if possible.
- Turn on the range hood while cooking on the stove or in the oven. Leave it on for 10-20 minutes after you are done cooking.
- Cook on the back burners whenever possible. This will improve air flow to the hood and reduce the amount of PM released to your kitchen or living space.
- When cooking without a range hood:
- Open windows or doors (when safe) to bring fresh air indoors. This will help remove or dilute the PM in your kitchen.
- Turn on a wall or ceiling exhaust fan while cooking, if possible. This will improve the flow of PM and other cooking fumes to the outdoors.
- Reduce the amount of PM that is released while cooking:
- Don’t deliberately burn or char food indoors.
- Set burners at lower temperatures, when possible.
- Use cooking oils with higher smoke points when cooking at high temperatures. Canola oil and peanut oil both have high smoke points.
- Routinely clean kitchen surfaces and cooking appliances (e.g., toaster, stove, burners, oven, microwave, pots and pans). This will reduce the chances of accidently heating or burning crumbs and creating more PM.
- Install a range hood. Preferably one that vents to the outside.
- If you do not already have a range hood, consider installing one over your stove. The best choice is a range hood that vents to the outdoors instead of one that just recirculates the air. If your home does not have an outside exhaust vent, consider consulting with a contractor to see if one can be installed.
- Choose a range hood with the appropriate airflow rate for your home.
Some key things to look for when selecting a range hood are sufficient airflow (usually provided in cubic feet per minute, or cfm) and low noise (usually provided in sones). The ROCIS Initiative provides more information about selecting an effective ducted range hood
Caution:
In some cases, range hoods with high airflow rates can cause a serious problem known as combustion appliance backdrafting. Combustion backdrafting occurs when more air is exhausted to the outside than is brought in. This can disrupt the normal airflow from a natural draft combustion appliance, such as a gas water heater or furnace, causing harmful carbon monoxide and combustion products to be drawn into living areas. Consult a professional if you need help selecting or installing a range hood and/or preventing combustion backdrafting.
Additional Resources
- California Air Resources Board - Indoor Air Pollution from Cooking
- Lawrence Berkeley National Laboratory - Looking for Hazardous Pollutants in Your Kitchen, Video by Dr. Brett Singer
- ROCIS Initiative - Kitchen Range Hoods
- Lawrence Berkeley National Laboratory - Addressing Kitchen Contaminants for Healthy, Low-Energy Homes
- Environmental Law Institute - Reducing Exposure to Cooking Pollutants: Policies and Practices to Improve Air Quality in Homes
Combustion and Heating
Burning or combusting almost anything produces PM. Tobacco and other smoking products, heating and cooking appliances, candles, and fireplaces can all produce PM. These sources can also release harmful combustion byproducts, such as carbon monoxide, directly into the indoor environment. Secondhand smoke also contains PM.
Actions You Can Take
- Do not allow smoking in your home. If you or a family member smoke, do it outside and away from windows, doors and outdoor air intakes that can draw the smoke into your home.
- Ensure proper ventilation is available when burning candles and incense indoors.
- Never use a charcoal or hibachi grill indoors.
- Vent all fuel-fired combustion appliances to the outdoors (including gas, coal, oil and wood-burning stoves, heaters, and furnaces).
- Install and use exhaust fans vented to the outside when cooking.
- Avoid the use of unvented combustion appliances indoors. This includes stoves, fireplaces, or fuel-powered space heaters. If you must use unvented appliances, follow the manufacturer’s instructions, including those related to ventilation.
- Have a trained professional inspect, clean and tune-up your central heating system (furnace, flues, and chimneys) annually. Repair any leaks promptly.
- Choose a wood-burning appliance that is certified to meet EPA emission standards.
- Keep the doors of wood-burning appliances closed, unless loading or stoking the live fire.
- Use dry, seasoned wood in stoves and fireplaces. Provide sufficient air to the fire so that it does not smolder. Learn more about the best wood-burning practices.
Additional Resources
Indoor Dust
Indoor dust is settled PM from a variety of sources. It can be easily kicked up into the air by cleaning, vacuuming, and other activities like walking and crawling. Children are exposed to more indoor dust than adults. This is because they crawl and play closer to the floor, where the dust that accumulates on surfaces can be inhaled more easily. Also, they often put their hands, toys, and other items into their mouths. Children also eat, breathe, and drink more relative to their body mass than adults do.
Indoor dust may contain:
- Outdoor soil and dust that has been blown or tracked indoors;
- Biological particles, also known as biological contaminants, including pollen, mold spores, pet dander, dust mites, and human skin flakes and hair;
- Particles from human activities, such as cooking, cleaning, and burning candles;
- Particles from consumer and personal care products;
- Plastics, flame retardants, and pesticides; and
- Sometimes industrial chemicals and heavy metals, such as lead.
Actions You Can Take
- Frequent cleaning and ventilation are effective ways to reduce dust and other pollutants.
- Vacuum carpets and furniture every week, or more often.
- Dust often with a damp cloth. Dampening the cloth helps keep settled dust from going back into the air.
- Consider using a vacuum with a HEPA filter to reduce dust build-up. A HEPA filter can help keep some vacuumed dust from escaping the vacuum cleaner back into the air.
- People with asthma or allergies should leave the area being vacuumed to avoid breathing in dust that is stirred up during vacuuming.
- Routinely change air filters in HVAC systems (central heating and cooling systems) and in portable air cleaners according to the manufacturer's directions.
- Upgrade HVAC filters. Higher-efficiency filters in central heating and cooling systems and portable air cleaners can reduce harmful pollutants such as indoor PM. You can learn more about air cleaners and air filters in the home.
- Take steps to prevent and reduce exposure to biological contaminants.
- If your home contains lead or asbestos, you should use extra caution and take additional steps to safely address indoor dust concerns.
- If you are remodeling your home, follow best practices for indoor air quality to contain dust and other pollutants while you work.
Additional Resources
Biological Contaminants
Biological contaminants are commonly found in indoor dust and may include pollen, mold spores, pet dander, dust mite and cockroach droppings, and human skin cells. Walking, sweeping, dusting and vacuuming can stir dust up into the air. In addition, water or moisture problems can lead to mold growth indoors. Many biological contaminants, including mold, contain allergens. Minimizing exposure to PM that contains allergens is especially important for those with asthma because they can trigger asthma symptoms. Take steps to prevent and reduce exposure to biological contaminants.
Actions You Can Take
- Keep your windows closed on high pollen days.
- Frequent cleaning is an effective way to reduce the buildup of indoor dust and allergens, including from dust mites and animal dander:
- Vacuum carpets and furniture every week, or more often.
- Dust often with a damp cloth. Dampening the cloth helps keep settled dust from going back into the air.
- Consider using a vacuum with a HEPA filter to reduce dust build-up. A HEPA filter can help keep some vacuumed dust from escaping the vacuum cleaner back into the air.
- People with asthma or allergies should leave the area being vacuumed to avoid breathing in dust that is stirred up during vacuuming.
- Wash bedding in hot water once a week, and dry completely.
- Use dust proof covers on pillows and mattresses.
- Choose stuffed toys that you can wash. Wash stuffed toys in hot water. Dry completely before your child plays with the toy.
- Keep your home dry to prevent mold, dust mites, and cockroaches.
- To prevent mold growth, fix water problems quickly. Dry damp or wet items within 24-48 hours. Learn more about mold cleanup in your home and mold, moisture and IAQ.
- Keep indoor humidity low. If possible, keep indoor relative humidity below 60% (ideally between 30%-50%).
- Condensation can be a sign of high humidity. If you see condensation or moisture collecting on windows, walls or pipes, act quickly to reduce the moisture or water source and dry the wet surface. See more tips for controlling humidity and preventing condensation.
- To reduce indoor humidity, install and use exhaust fans that are vented to the outdoors in kitchens and bathrooms.
- Vent clothes dryers outdoors.
- If you use cool mist or ultrasonic humidifiers, clean them according to the manufacturer's instructions. Consider using distilled water to reduce the potential for dispersing minerals into the air. Learn more about the use and care of home humidifiers.
Additional Resources
Consumer Products
Many products used in the home, including cleaning solutions, air fresheners, and personal care products can contribute to indoor PM. When these products are used, they or their byproducts can react with other chemicals in the air or on surfaces to form PM and other air pollutants. For example, air fresheners, cleaning products and fragrances that have a pine or citrus scent can react with ozone to form PM and formaldehyde in indoor environments. Additionally, some products such as cleaners, paints, adhesives, pesticides, cosmetics and air fresheners contain chemical irritants that may exacerbate asthma. At sufficient concentrations in the air, many products can trigger asthma.
Actions You can Take
- Make sure your child and anyone else that may be sensitive to these products are not around when they are being used.
- Always follow the instructions on the product label. Do not mix products, unless directed on the label.
- If you experience health symptoms when using a certain product, consult with your doctor and consider trying a different product.
- Open windows or doors and/or use an exhaust fan to ensure adequate ventilation when using these products.
- Never use chemicals intended for outdoor use, like certain pesticides, inside your home.
Additional Resources
Printers and Copiers
Some equipment, such as some copiers, laser-jet printers, and 3D printers can generate PM directly. Printers and copiers can also generate other harmful pollutants such as volatile organic compounds (VOCs). VOCs can then react with other chemicals in the air or on surfaces to form more PM. Several strategies in combination with increased filtration and ventilation can reduce your exposure to indoor PM from printers and copiers.
Actions You Can Take
- Open windows or doors and/or use a local exhaust fan when operating printers or copiers. Do not operate these devices in poorly ventilated spaces.
- Consider using a portable air cleaner and/or upgrading the air filter in your furnace or central heating, ventilation, and air-conditioning (HVAC) system to improve indoor air quality.
- When using a 3D printer:
- Use 3D printers and materials with lower emissions.
- Reduce the printer nozzle temperature.
- Reduce time spent near the printer while it is running. Use video monitoring to check progress from another room.
- If your 3D printer does not have an enclosure, consider placing one over the 3D printer to contain the particles. An enclosure may help control the number of particles released into the air. For further reduction, consider supplying the enclosure with its own local exhaust ventilation.
Additional Resources
- CDC/NIOSH - 3D Printing Safety at Work
- CDC/NIOSH - Additive Manufacturing/3D Printing
- Keeping up with 3D Printing: EPA Researchers Build on New Plastic Emissions Study
- EPA Researchers Continue to Study the Emissions of 3D Printers
- Chemical Insights, an Institute of Underwriters Laboratories - Research on Chemical and Particle Emissions from 3D Printing
Hobbies
Hobbies that involve working with wood, metal or products such as glues and adhesives can generate PM.
Hobbies involving wood-working and metal-working can produce large quantities of PM in the form of dust. When precautions are not taken, wood- and metal-working can lead to hazardous exposures. Wood dust is considered a human carcinogen. Exposure to excessive amounts of wood dust can irritate the eyes, nose, and throat. Exposure to wood dust can also reduce lung function. Western red cedar dust has been shown to cause asthma. Significant accumulations of fine particles of wood dust can also be a fire and explosion hazard.
Hobbies involving glues, adhesives, paints, permanent markers, and photographic solutions, such as those commonly used in arts and crafts, can generate PM and VOCs. More PM may be produced when the VOCs react with other chemicals in the air or on surfaces to create PM.
Actions You Can Take
- Always follow the instructions on the product label, when using materials, chemicals, or devices. This includes any recommended personal protective equipment.
- Open windows or doors and/or use a local exhaust fan to increase ventilation.
- Don’t work in poorly ventilated spaces.
- Use a portable air cleaner and upgrade your HVAC filter. Learn more about air cleaners and filters.
Additional Resources