Sensgreen Knowledge Base

Particulate Matter (PM)

What Is Particulate Matter (PM)?

Particulate Matter is the general name of solid or liquid particles that are smaller than 10 μm as defined by the ASHRAE. Depending on the particles’ size, they are named PM10, PM₄, and PM2.5, accordingly. Current information indicates that small particles (commonly measured as PM2.5) are strongly related to mortality and cardio-pulmonary diseases, stated by WHO (World Health Organization).


They're Small, But How Small Actually?

PM10 are inhalable particles, with diameters that are generally 10μm (micrometers) and smaller, and PM2.5, are fine inhalable particles, with diameters that are 2.5 μm (micrometers) and smaller. How small are 2.5 μm? Think about a single hair from your head. The average human hair is about 70μm  in diameter – making it 30 times larger than the largest fine particle.¹

Some common examples of these particles are smoke, dust, dirt, domestic animal allergens, lint, pollen, mold spores, bacteria, and some airborne viral particles.

Sources of Particulate Matter

Indoor sources of particulate matter can be different.  Ignition-related activities like cooking, fireplaces, stoves, cooking, or smoking can be the source of particulate matter indoors. 

While these are the possible indoor sources of PM, they can get inside your building from outside via construction and demolishing activities nearby, industrial processes, or from the vehicles passing by combustion of fossil fuels. ²

But generally, indoor areas expected to have the same or lower levels of PM in comparison to surrounding outdoor spaces.


Distribution of Particular Matter from All Continental Sources (Excluding Sea Salt Emissions), 1998 ( Adapted from U.S. EPA, "Air Quality Criteria for Particular Matter." Available from


Heart and Lung Diseases

Other Effects of Particulate Matter on Human Health

Exposure to particulate matter can cause serious health problems, including premature death for people with lung or heart diseases, nonfatal heart attacks, decreased lung function, and irregular heartbeat.³

Additionally, according to an article published by WHO, exposure to PM2.5 reduces the population’s life expectancy by ≌9 months. Furthermore, PM is responsible for 3% of cardiopulmonary and 5% of lung cancer deaths globally. ⁴

On top of these, according to research from Harvard University, fossil fuel pollution caused more than 8 million deaths in the year 2018. In the same research, it is also estimated that particulate matter exposure from these fossil fuel emissions is also responsible for 18% of the total global deaths for the same year. ⁵


The severity of Particulate Matter Levels on COVID-19

The rapid spread of the SARS-CoV-2 during the COVID-19 pandemic had raised questions on the route of transmission of this disease. The initial understanding was that transmission originated from respiratory droplets from an infected host to a susceptible host. However, indirect contact transmission with the viable viruses by different sizes of particles has been suggested.  A 10 μg/ increase of pollution level was associated with an 8.1%-11.5% increase in the number of cases, for PM2.5 and PM10 respectively. ⁶



How To Protect Yourself From PM When Indoors?

The first step is to track outdoor PM levels regularly. Depending on outdoor levels, window usage should be limited. However keeping outdoor particles outside is not enough, because there are indoor sources of PM2.5 and PM10.

Traditional air filters like HEPA are rated to remove 99.97% of particles 0.3 μm in size. However, HEPA filters are congested due to holding airborne dirt over time. You can track your HEPA filter performance by comparing indoor and outdoor environment PM2.5 and PM10 levels continuously.  Additionally, smoking is one of the biggest indoor particulate matter sources. Only one cigarette can increase PM level to 100 μg/, which is 4 times higher than the acceptable PM level according to WHO. ⁷

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