Comprehensive Guide to PM2.5 Filters for Face Masks & Face Covers

Comprehensive Guide to PM2.5 Filters for Face Masks & Face Covers

A PM2.5 filter is a mask insert that can be inserted into the inner pocket of a cloth mask to increase it’s filtering performance. It gets its name from an established standard based on  2.5 micrometers (microns) – equivalent to 0.0025 mm – a reference to the size of airborne particulate matter that this filter is targeted for.

It is made up of five filtration layers, including a middle layer of activated carbon, that work together to achieve superior filtration performance. Note that no mask is 100% protective against COVID-19 virus; the use of masks is still encouraged by public health officials in many jurisdictions. While the most recommended type of mask is an N95 mask, they are hard to come by given the increased demand during the pandemic.

What is a PM2.5 filter?

PM2.5 is an ISO standard referring to tiny airborne particulate matter that are the less than 2.5 microns (0.0025mm) wide – or 3% the size of human hair. A PM2.5 filter is designed to filter airborne particulate matter smaller than 2.5 microns. ISO describes the efficiency of such filters to be capable of filtering particle sizes in the range of 0.3 microns to 2.5 microns.

What are PM2.5 filters made of?

The filter consists of five layers of activated carbon filter and different kinds of fabric:

  • Layers 1and 5: Spun-bound non woven material that filters out larger particles
  • Layer 3(middle): activated carbon layer. Traps particulate matter via an adhesion process.
  • Layers 2and 4: high-efficiency melt-blown filtering material that can filter small substances.


How is a PM2.5 filter used?

It is really simple to use this filter. Simply insert the filter in the inner pocket of your cloth mask!

How long will a PM2.5 filter last?

The PM2.5 filter longevity will depend on, of course, how much it is used and the intensity of particulate matter in the environment it is used. In a highly polluted city, or during forest fire haze, it will probably last 3-4 uses due to the higher concentrations of particulate matter.

How often should a PM2.5 filter be changed?

Ideally after every single use. However, it all depends on your use patterns as indicated above. It is recommended that the filter be replaced after a maximum of 12 hours of use.

Why use a PM2.5 filter?

The best type of mask recommended for use during the COVID-19 pandemic is an N95 mask. These masks are functionally equivalent to KN95 respirators in China and FFP2 respirators in Europe. That is why they are the preferred choice for healthcare workers.

N95 respirators get their name from the fact that they are officially certified by the National Institute for Occupational Safety and Health (NIOSH) to have a 95% minimum efficiency level for trapping airborne particles when properly used.

It would be nice if we all could get one. However, there are three reasons why we can’t and therefore should probably look at other alternatives to N95 masks:

  1. N95 masks are most-needed in healthcare settings for use by front line healthcare workers who are looking after COVID-19 patients. Given the risk of this work, I think we would all agree that it is best to leave the best equipment, mask to these professionals, as well as others in high risk occupations. There is already a significant shortage worldwide. Those in high risk occupations should get priority on accessing N95 masks produced.
  2. There is an acute shortage of N95 masks worldwide. Even if you wanted one, chances are it would be difficult to find one. Even if you find one, often times it will be pricey.
  3. The third reason is: N95 have to be used properly for you to benefit from their protection. Fit testing is key to ensure the mask has a proper closed fit. Healthcare workers actually have to get trained on this in addition to other personal protective equipment. Therefore, it would be something that would be difficult to educate the whole public on. This opens up the risk of someone using these masks having a false sense of security if they are not using the correctly.

PM2.5 filter used together with a cloth mask is therefore a great alternative since it still offers a high degree of filtration performance. In addition, using a PM2.5 filter and cloth mask combination imposes only 25% of inhalation resistance compared to a properly fitted N95 mask – which is typically tight-fitted.

Can I reuse a PM2.5 filter?

It is recommended that PM2.5 filters be used for a maximum of 12 hours.  PM2.5 are not washable nor can they be remediated for reuse. Any washing or attempts at cleaning may reduce the performance of the filter.

What are other benefits of PM2.5 filter?

PM2.5 filters are effective against small particulate matter pollution. There is significant scientific evidence about the effect of PM2.5 to our health.

PM2.5 filters can be useful in significantly reducing exposure to tiny particulate matter. This is even more important for those with allergies, asthma, lung diseases, expectant mothers who want to reduce exposure to environmental toxins, children and the elderly etc.


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