Fine particulate matter

On this page

Health effects

Fine particulate matter is most dangerous for the following at-risk groups:

  • children with asthma because it affects breathing functions
  • older adults because it affects breathing, heart and blood functions
  • people with an underlying breathing and/or heart condition because it worsens their condition(s)

Indoor sources

Particulate matter that is present indoors consists of a mixture of substances, such as:

  • pollen
  • fungal spores
  • endotoxin (a toxin present in bacteria)
  • tiny liquid or solid particles in aerosols
  • carbon (soot) produced when materials are burned
  • different chemical pollutants that attach to particles

In a properly maintained home, a lot of the fine particulate matter:

  • comes from outdoors
  • seeps in through:
    • ventilation systems
    • open windows and doors
    • air leakage from cracks and holes in the building

The most common indoor sources of fine particulate matter include:

Other sources of indoor fine particulate matter include:

  • hobbies and renovation activities that create dust, like cutting or sanding wood
  • disturbing particles that have settled on surfaces while:
    • dusting with a dry cloth or a feather brush
    • vacuuming with a vacuum that does not have a HEPA filter
    • sweeping with a broom
  • furnaces, wood stoves or fireplaces that are improperly installed or maintained
  • smoke produced from burning candles and incense, especially when the flame is put out

Reduce exposure in the home

The best way to reduce fine particulate matter indoors is to:

  • remove sources that produce it
  • reduce how much sources produce

Ways to reduce exposure to fine particulate matter in your home include:

  • cleaning with a:
    • mop
    • damp cloth
    • HEPA vacuum
  • keeping your home free of tobacco smoke
  • reducing the use of candles and incense in your home
    • use a snuffer to extinguish candles instead of blowing them out
  • moving dusty work outside, for example:
    • cutting and sanding outdoors for renovation projects
    • using a local exhaust system vented to the outside when you do hobby work indoors like wood working with power tools
  • ensuring furnaces, wood stoves and fireplaces are installed and working properly
    • have chimneys cleaned annually
    • follow manufacturers' directions for maintenance
  • using the exhaust fan every time you cook (or the range hood fan if equipped)
    • make sure it is properly installed and maintained
  • controlling humidity to prevent mould growth

Never idle your vehicles in your attached garage or near doors and windows.

Also, never use a barbecue or generator indoors or in your attached garage.

Canada has developed an indoor air quality guidance document for fine particulate matter in homes.


Ventilation can help reduce indoor fine particulate matter levels by removing emissions from indoor sources like cooking.

You should consider the following if you have a home furnace or heating, ventilation and air-conditioning (HVAC) system.

  • Some furnace filters can help to remove fine particulate matter.
  • Having a heat recovery ventilator as part of your HVAC system can help reduce fine particulate matter levels.
    • It is designed to bring in fresh, filtered outside air.

Removal rates for filters can change over time. It is important to replace or clean filters regularly as per manufacturers' instructions.

Outdoor particulate matter levels may often be higher than indoor levels. Therefore, natural ventilation (from an open window or door) may not always be effective in reducing indoor levels. This is especially the case on poor air quality days, so use an air conditioner when it is smoggy outside, if possible.

For information on outdoor air quality in your area, you can consult the:

Air cleaners

Portable air cleaners can also lower indoor fine particulate matter levels. Examples of devices include:

  • high efficiency particle air (HEPA) filters
  • electrostatic precipitators

While electrostatic precipitators can reduce airborne particles, some may also produce ozone (a lung irritant) as a by-product. When choosing an electrostatic precipitator, look for those that are certified as only releasing low amounts of ozone. This would include air cleaners that are certified by the California Air Resources Board (CARB) or those which meet the CSA standard or ozone. If the air cleaner claims to meet a CSA standard, make sure it refers to the ozone standard (known as CSA standard 22.2 187-15).

HEPA filters and electrostatic precipitators should only be used along with:

  • good ventilation
  • reducing and eliminating indoor sources of fine particulate matter

Factors you should consider when buying a portable air cleaner include the:

  • capacity of the air cleaner in relation to the size of the room it is used in (clean air delivery rate)
  • efficiency (effectiveness) of the filter in capturing particles of different sizes
    • look for filters designed to capture fine particulate matter

About fine particulate matter

Fine particulate matter is the name for a range of particles that are less than 2.5 microns (µm) in diameter. This is why it is often referred to as PM2.5.

These particles are part of a wider range of particles called particulate matter. Particulate matter:

  • can be solid, liquid or a mixture of both
  • is small enough to be carried by air and breathed into your lungs
  • range from 0.005 to 100 microns in diameter
    • as a comparison, the average diameter of a human hair is 60 microns

Fine particulate matter is so small that you cannot see it without a microscope. These particles are a greater threat to human health because they can travel deeper into the lungs.

Related links

Page details

Date modified: