Below 15µg/m3

Particulate Matter also known as “Particle  Pollution” is a complex mixture of extremely small  particles and liquid droplets. Particulate Matter at  2.5 microns in size or smaller can be inhaled deep  into the lungs and cause irritation and corrosion of  the alveolar wall, which impairs lung function3.  They are also known to carry microbiomes4. 

These particles are small enough to stay  suspended in the air. A study conducted by Feng,  Cindy et al published in the Journal of  Environmental Health5 showed an increased  vulnerability to influenza-like illnesses when levels  of PM2.5 were above the ideal range. The data  suggests that PM2.5 stays airborne longer,  creating a “condensation nuclei” which virus  droplets attach to. These are then inhaled by  people, resulting in infection.

Thus, it is best to keep your PM2.5 levels low to  minimize risk of infection.

Examples of sources of PM2.5 indoors: smoking,  cooking, candles, space heaters, furnaces, and  poorly-maintained HVAC system.