What is PM2.5 Particulate Matter?

PM 2.5 pertains to dust, particulates, spores, and pollen in the air. PM2. 5 refers to particles that have a diameter less than 2.5 micrometres which is more than 100 times thinner than a human hair and remain suspended and floating longer in the air. Many of these particles are formed as a result of burning fuel and chemical reactions that take place in the atmosphere. 

Particulate Matter 2.5, the smallest and most dangerous form of air pollution.  Airborne virions are even smaller than PM2.5 (the Coronavirus's lipid envelope is about 120 nanometers across). However, since the virus is not aerosolized (airborne) it sticks to water droplets and other particles that are much larger (>5 microns).  

NIH research has shown PM2.5 charcoal activated material to capture nanoparticles of this size with a high degree of efficiency (approx. 95%), and lab tests show a PM2.5 filter with a properly-fitted cloth mask can reduce total airborne particulates by as much as 90%,

Although no mask can guarantee 100% protection from any virus or pathogen, wearing a properly fitting cotton mask with a PM2.5 filter will reduce your exposure as shown above.

How is PM2.5 Measured?

PM2.5 refers to atmospheric particulate matter (PM) that have a diameter of less than 2.5 micrometers, which is about 3% the diameter of a human hair.

Commonly written as PM2.5, particles in this category are so small that they can only be seen with a microscope. They are even smaller than their counterparts PM10, which are particles that are 10 micrometres or less, and are also called fine particles.

Due to the many adverse effects fine particles can inflict on a large number of people, PM2.5 is one of the major pollutants closely monitored by health authorities around the world. You will most likely come across a dedicated column for PM2.5 alongside the Air Quality Index (AQI), Pollutants Standards Index (PSI) or the air quality standards adopted by your country.

On a very clear and non-hazy day, the PM2.5 concentration can be as low as 5 µg/m3 or below. The 24-hour concentration of PM2.5 is considered unhealthy when it rises above 35.4 µg/m3.

Why 24-hour and not a shorter duration when evaluating the health impact of fine particles? This is because the potential damage caused by air pollutants depends not just on the concentration, but also on the duration of exposure. The longer you are exposed to PM2.5, the higher the risk of developing adverse effects caused by the exposure. That’s why a 24-hour measurement is a better reflection of the health effects of fine particles than say a three-hour reading.

The table below will give you a sense of what levels of PM2.5 are harmful and the appropriate precautions you need to take. It is based on the air quality standards for particle pollution published by the U.S. Environmental Protection Agency.

24-Hour PM2.5 Levels (µg/m3)

Air Quality Index
PM2.5 Health Effects
Precautionary Actions
0 to 12.0
0 to 50
Little to no risk.None.
12.1 to 35.4
51 to 100
Unusually sensitive individuals may experience respiratory symptoms.Unusually sensitive people should consider reducing prolonged or heavy exertion.
35.5 to 55.4
Unhealthy for Sensitive Groups
101 to 150
Increasing likelihood of respiratory symptoms in sensitive individuals, aggravation of heart or lung disease and premature mortality in persons with cardiopulmonary disease and the elderly.People with respiratory or heart disease, the elderly and children should limit prolonged exertion.
55.5 to 150.4
151 to 200
Increased aggravation of heart or lung disease and premature mortality in persons with cardiopulmonary disease and the elderly; increased respiratory effects in general population.People with respiratory or heart disease, the elderly and children should avoid prolonged exertion; everyone else should limit prolonged exertion.
150.5 to 250.4
Very Unhealthy
201 to 300
Significant aggravation of heart or lung disease and premature mortality in persons with cardiopulmonary disease and the elderly; significant increase in respiratory effects in general population.People with respiratory or heart disease, the elderly and children should avoid any outdoor activity; everyone else should avoid prolonged exertion.
250.5 to 500.4
301 to 500
Serious aggravation of heart or lung disease and premature mortality in persons with cardiopulmonary disease and the elderly; serious risk of respiratory effects in general population.Everyone should avoid any outdoor exertion; people with respiratory or heart disease, the elderly and children should remain indoors.

Source: U.S. Environmental Protection Agency

Why is PM2.5 Harmful?

PM2.5 Particulate Matter is harmful since these particles are so small, light and very fine particles. They have the ability to stay longer in the air as compared to the heavier particles. 

PM2.5 in the air reduce visibility and cause the air to appear hazy when levels are elevated. PM 2.5 tends to stay suspended in the air longer thus can lead to plaque deposits in your nose, throat, lungs or even the arteries and can even lead to a heart attack.

They become dangerous when these particles that are smaller than 2.5 micrometres will be able to make their way to the nose, throat and penetrate deeply into the lungs and the worst scenario if some might be able to enter the circulatory system.

Other reasons why PM2.5 Particulate Matter is dangerous because it has multiple short terms and long term health impacts. The short term might include irritation in the eyes, nose and throat, coughing, sneezing and shortness of breath.

Prolonged exposure to PM2.5 can cause permanent respiratory problems such as asthma, chronic bronchitis and heart disease.  While PM2.5 impacts everyone, people with breathing and heart problems, it’s the children and the elderly that are most sensitive to it.  The continuous exposure to particulate matter can be put your health in the line for it’s said to be lethal than alcohol and diabetes.

Always protect yourself in situations that can expose you to the ills of PM 2.5. Wear a mask and be safe.

PM2.5 Filters - How do They Work?

PM2.5 filters are made from the same advanced materials used for respirators like the N95 and KN95, in addition to activated carbon fabric. A quality carbon PM2.5 filter is made up of three non-woven materials: spun-bond fiber, melt-blown fabric, and activated carbon fabric. 

Melt-blown fabric acts as a physical barrier against microscopic particulates while also providing an electrostatic barrier to stop aerosolized nano-particles.  Melt-blown fabric is softer and less rigid than spun-bond. It almost looks like pulped tissue paper, as opposed to the plastic-sheen of spun-bond.  Activated carbon fabric has multiple benefits, including acting as a natural de-odorizer and anti-microbial in addition to its electrostatic properties.

PM2.5 Filtered Masks vs. N95 or KN95

When combined with a fitted adjustable cotton masks like the BZMask Sigma Series FaceShields and Delta Series masks, PM2.5 filters can block the vast majority of airborne particulates, with significantly less inhalation resistance than a sealed n95/kn95 respirator. In laboratory testing, cotton masks with PM2.5 filters restricted inhalation by less than than 71 Pa, 343 Pa.

There are three levels of oil resistance on respirator masks.  N refers to masks that are Not resistant to Oil.  R refers to masks that are Resistant some oils.  P refers to masks that are oil Proof.

There are three levels of filtration on respirator masks.  95 masks filter 95% of particulate matter at .3 microns when properly fitted and used.  97 masks filter 97% and 99 provide the maximum filtration level of 99% at the .3 micron level.

Therefore an N95 respirator is a mask that when properly fitted and used is Not oil resistant and filters 95% of particulate matter .1 microns or greater.

N95 respirators are tight-fitting respirators that filter out at least 95% of particles in the air greater than .3 microns, including large and small particles. Not everyone is able to wear a respirator due to medical conditions that may be made worse when breathing through a respirator. Before using a respirator or getting fit-tested, workers must have a medical evaluation to make sure that they are able to wear a respirator safely. Achieving an adequate seal to the face is essential. A true N95 respirator mask is approved by the National Institute Of Safety and Health (NIOSH), is  tested and rated mask that can filter out 95% >2.5 micron dust and particulates in the air.   These N95 Respirators are generally reserved for industrial and medical use and require a proper fitting and testing environment not available to most end-users.

The difference between an N95 and a KN95 mask is where the mask is certified. Much like other industries, respirators/masks have different approval sources and names.

  • Australia/New Zealand- P2
  • Brazil- P2
  • China- KN95, KP95
  • Europe-FFP2
  • Japan-DS2, DL2
  • India-BIS P2
  • Korea- 1st class
  • US- NIOSH N95, R95, P95

KN95 masks are regulated by the Chinese government under regulation GB2626-2006 and are rated to filter 95% of particles. In April of 2020, in order to help expand the availability of general use face masks for the general public and particulate filtering facepiece respirators for healthcare professionals during the COVID-19 pandemic, the FDA issued guidance authorizing the use of KN95 masks as suitable NIOSH alternatives under certain emergency circumstances (Source:FDA  https://www.fda.gov/medical-devices/personal-protective-equipment-infection-control/faqs-shortages-surgical-masks-and-gowns and FDA https://www.fda.gov/media/136449/download).

On May 7th of 2020, the FDA updated the April guidance and issued further guidance limiting the use of certain KN95 masks as suitable NIOSH alternatives in a healthcare setting (Source: FDA https://www.fda.gov/media/136664/download).

Other differences between N95 masks vs KN95 masks are that KN95 masks often use the earloop method of wearing the respirator whereas the N95 masks use a two head-strap attachments, one that goes around the back of the head under the ears and another that goes on the top over the crown of the head above the ears. It really comes down to personal preference in terms of which one is more comfortable for the wearer as well as the level of safety and protection one feels is necessary given the particular activity being carried out.