What Is a PM 2.5 Filter?

With people all over the world increasingly dealing with the effects of air pollution, there has been a rise in interest in the quality of the air we breathe in our homes, as well as the options available to protect ourselves from exposure to pollutants and viral pathogens in public spaces. PM 2.5 filters have become a popular talking point, with many people debating the efficacy of using these filters as disposable inserts in their masks.

Why all the hype? A PM 2.5 filter creates an electrostatic barrier that catches and blocks tiny particles that other materials such as cotton and polyester can’t adequately block.

In other words, using a PM 2.5 filter in your mask or other device is a good way to increase your protection from harmful airborne pathogens and other particulates. But what is PM 2.5, and how do PM 2.5 filters work?

What Is PM 2.5?

PM stands for particulate matter, which is a mixture of liquid and solid particles in the air. 2.5 refers to the diameter of particulate matter – less than 2.5 microns – which is the smallest measurement of air pollution.

How small? Think of it this way: the width of a human hair is about 50 microns. Particles measuring 2.5 microns or less are too small to be seen with the naked eye, but can nevertheless present a serious health risk when breathed in – even over short periods of time. Why?

Airborne particles or droplets measuring PM 2.5 or less are particularly dangerous because they can penetrate deep into your lungs. Particles this small can get around the body’s natural defense systems, such as nose hair and mucus, then enter the lungs, and eventually be absorbed into the bloodstream.

Large airborne particles measuring PM 10 or more can cause irritation to your eyes, nose and throat, and can cause respiratory diseases over time, but they are comparatively less dangerous for your health because they are too big to enter your lung tissue in large quantities.

While PM 2.5 pollution is dangerous long-term for everyone, it’s especially risky for children, the elderly, and anyone with preexisting cardiovascular or lung diseases.

Sources of PM 2.5

PM 2.5 particles are unique from other airborne particles because they can be made from both solid and liquid particles, and can be made from combinations of different materials flying in the air. Certain natural disasters, such as wildfires and volcanic eruptions, are known to release particles registering as PM 2.5 into the air.

In addition to natural disasters, man-made sources of PM 2.5 pollutants include industrial factories and power plants, coal combustion, burning biomass, and fossil fuel-burning vehicles.

While most PM 2.5 pollutants come from outside your home, there are also indoor sources of PM 2.5 pollution, including fireplaces, wood-burning stoves, and potentially even candles.

A PM 2.5 filter in a mask is a must if you live in an area with high levels of industrial air pollution, or if a natural disaster such as a wildfire has created unsafe levels of particulate material in the air. Accordingly, it’s important to know the quality of the air in your area on any given day.

Measuring Air Quality

Not sure what the air quality is like in your area? The World Air Quality Index hosts a live map on their website, with real-time updates from most cities and human-inhabited areas around the world.

The Air Quality Index (AQI), a standardized index for measuring the level of pollution in the air, is divided into six zones, running from 0 to 50.

  • 1-50: Air quality is excellent, with basically no risk to anyone.
  • 51-100: Air quality is moderate, with minor risk for people with severe allergies or sensitivities.
  • 100-150: Air quality is unhealthy for sensitive groups.
  • 151-200: Air quality is unhealthy, and may pose health risks for the general public.
  • 201-300: Air quality is very unhealthy, and a general alert should be declared warning of health risks for all.
  • 300-500: Air quality is hazardous, and represents an emergency situation.

To put it simply, the lower the AQI score, the healthier the air outside is. If you are particularly sensitive to air pollutants or suffer from asthma or other respiratory illnesses, it’s a good idea to start wearing a mask with a PM 2.5 filter at around 150 AQI. If the air in your area passes 200 AQI, it’s time to put on a PM 2.5 filter no matter who you are.

The Air Quality Index looks at five different indicators to measure overall air quality:

  • Particulate matter (also known as particle pollution. This includes PM 2.5 and PM 10)
  • Ground-level ozone
  • Carbon monoxide
  • Sulfur dioxide
  • Nitrogen dioxide

All of these substances are harmful to human health in varying amounts, and a PM 2.5 filter mask can go a long way towards keeping you healthy when the air quality outside hits unsafe levels.

PM 2.5 Filters

PM 2.5 filters come in a variety of forms and sizes, and some are more effective than others. Let’s take a look at how they’re made, and what to look for in terms of quality.

A high-quality PM 2.5 filter should be made out of three non-woven materials:

  • Melt-blown polypropylene fabric
  • Spun-bond polypropylene fabric
  • Activated carbon fabric

Of these three layers, the most important is the melt-blown fabric. This acts as a barrier not only because it’s tightly non-porous (the benefit of non-woven fabric) but also by generating an electrostatic barrier. This prevents aerosolized nanoparticles from getting through the fabric.

Spun-bond fabric is another non-woven layer that provides structure while acting as a barrier to larger particles.

Finally, activated carbon fabric acts as a deodorizer and antibacterial layer, filtering out particles through a process called absorption.

These three elements together ensure an effective, high-quality PM 2.5 filter. When buying a PM 2.5 filter, a surefire sign of lower quality is a replacement of the important melt-blown fabric layer with spun-bond fabric. Although spun-bond fabric does a great job keeping out larger particles, it doesn’t generate the electrostatic layer essential for blocking tiny nanoparticles. For a PM 2.5 filter to be effective, it must include a melt-blown polypropylene component.

Note: If using as an insert in a face mask, it’s important to know that PM 2.5 filters can lose their efficacy over time, and should be replaced at least once every twenty-four hours.

How to Protect Yourself Against PM 2.5

Outdoors, wearing a mask with a PM 2.5 filter is an effective option for protecting yourself against harmful PM 2.5 pollution. However, if air quality levels are bad enough to warrant a warning, it’s best to stay indoors if at all possible.

Indoors, there are a few actions you can take to protect yourself.

  • Stay inside. If the air quality in your area is registering at 200 AQI or more, it’s best to stay inside. Close all windows, vents, or other openings that could allow polluted air in. If you have cracks underneath your doors, shove a damp towel between the door and the floor.
  • Turn on an air purifier. Air purifiers with HEPA filters are the only types that are effective for removing PM 2.5 pollutants from the air. Air purifiers with HEPA filtration systems can remove up to 99.7 percent of particles as small as .3 microns in size.
  • Get an air purifier for your car. If you need to travel by car at times when the air quality is at dangerous levels, an air purifier for your car is a great option to keep yourself protected and breathing easy. This is particularly essential for anyone with a long daily commute to work, or anyone who regularly drives long distances, such as commercial truck drivers.
  • Be careful about using the A/C when the AQI is unhealthy. Most air conditioners work by pulling in air from outside. If your A/C unit does not have a HEPA filtration system (most don’t), then you could be pulling polluted air into your home.
  • Don’t burn candles in closed spaces. Candles, incense, and any device that emits gas can also potentially be emitting PM 2.5 pollutants into your home. When using these devices, make sure to open a window or have another source of fresh air circulation.

The Overview

PM 2.5, or particulate matter 2.5, are tiny particles of pollutants. They present a particularly high health risk because of their size; they are able to evade the body’s defense systems and penetrate deeply into the lungs, ultimately entering the bloodstream.

There are many potential sources of PM 2.5, both man-made and natural. With the pandemic raging and high pollution events becoming increasingly common, PM 2.5 filters are now a popular option for those looking to protect their respiratory health. 

PM 2.5 filters function by creating an electrostatic barrier that repels tiny particulate matter. When buying a PM 2.5 filter for a mask, be sure to check that it’s made from a combination of three non-woven materials for maximum efficacy.

In your house, air purifiers with HEPA filters are an effective way to protect yourself from PM 2.5 pollutants.