How long do PM 2.5 Carbon Filters last?

How long do PM 2.5 Carbon Filters last?

You’ve probably heard the warning “do not use your disposable face masks and filters for too long” countless times already. But with most research and advisories focused on masks, there’s barely enough information to gauge how often you should change a PM2.5 mask filter. You’re not the only one left with no choice but to make vague guesses!

Airnex is committed to help people breathe clean, so we’ve rounded up expert testimonies, official publications, and academic researchers then mixed it with our years of experience in the field of air quality. The result? A data-packed guide on the lifespan and proper usage of PM2.5 filters.

In a rush? Skip over to the “How long does a PM2.5 Activated Carbon Filter last?” section below to learn about the factors that affect their performance, along with our recommended usage period depending on the activity you’re using it for.

How do PM2.5 Activated Carbon Filters work?

how do pm 2.5 filters works
This type of filter is designed to protect you against Particulate Matter 2.5 (PM2.5) which are fine particles in the air measuring at most two and a half microns in width. For reference on how small these sneaky killers could be, one inch equates to a whopping 25,000 microns. 

PM2.5 can be present both indoors and outdoors, usually produced by activities that involve combustion (e.g. from vehicle exhausts, power plants, fire places, tobacco smoke, etc.)

Upon making their way into your lungs, PM2.5 can trigger irritation, shortness of breath, runny nose, and sneezing. In worse cases, constant exposure can aggravate respiratory and cardiovascular diseases (e.g. lung cancer, chronic bronchitis, reduced heart and lung function, etc.)

This dangerous foe calls for a powerful protective mechanism. Here’s how PM2.5 Activated Carbon Filters provide a practical yet effective solution.

Good quality PM2.5 filters are equipped with a five-layer combo of non-woven fabric, melt-blown cotton, and activated carbon. They isolate air pollutants through the process of adsorption

Yup, that’s not a typo! Absorbent materials allow foreign substances to seep through it. For instance, sponges will soak in water to fill the spaces inside it. In contrast, particles will stick to the surface of the activated carbon sheet because of its adsorption properties. Pollutants will be chemically bonded with the filter, so they cannot be separated by washing the product.

Remember that activated carbon filters can get saturated over time. Once they reach their full capacity, their ability to trap pollutants become compromised. You might even notice discoloration and odor from used products. These are common signals that it’s time to replace your mask’s filter.

Apart from blocking out PM2.5, activated carbon filters can also protect you from other airborne contaminants such as pollen, smog, germs and bacteria, molds, and spores.


How to use PM2.5 Activated Carbon Filters

pm 2.5 filters

 Keep these pointers in mind to make sure that you’re getting the most protection out of PM2.5 Activated Carbon Filters:

Check sufficiency of carbon content

Beware of bogus products! There are a lot of brands that claim to work but actually have minimal traces of carbon. These substandard filters could cost cheaper, but they can get saturated so quickly. 

Take a couple of minutes to check if the PM2.5 filters you’re buying are backed by third-party lab tests on filtration efficiency.

Make sure they fit your masks

Regardless of how thick and carbon-packed your PM2.5 filters are, their protective capabilities can be compromised if they are not compatible with your face mask.

In fact, a study conducted in Beijing proved how poor facial fit greatly reduces filtration efficiency. Make sure to double check the dimensions of the PM2.5 filter before buying one.

Regularly replace your filters

When they reach their full saturation capacity, PM2.5 filters lose their effectiveness in trapping air pollutants. Our scientists have yet to develop a perfect formula to calculate how long this could take. 

For a rough estimate, check the manufacturer’s prescribed usage period for your filters. Or better yet, read on to this article’s next section for a comprehensive analysis on how long does a charcoal filter last in a face mask.

How long does a PM2.5 Activated Carbon Filter last?

pm 2.5 filters airnex


PM2.5 filters might be powerful protective equipment, but their adsorption properties also have its limits. We’ve mentioned earlier that prolonged use will eventually fill its activated carbon layer up with particles. When this limit is reached, they can no longer trap more pollutants so it's time to change your mask’s filter.

The lifespan of activated carbon filters mainly depends on its saturation capacity. According to the National Institute for Occupational Safety and Health’s (NIOSH) guidelines, the average amount of particles that disposable respirators can adsorb is about 200g.

This means that the frequency for replacing the PM2.5 filter in your mask depends on how fast the activity you’re using it for will load up the activated carbon layer.

For non-dusty workplaces, we recommend grabbing a fresh filter after 16-24 hours of total use. But if you’ll be exposed to very dusty activities (e.g woodworking, gardening, etc.) and environments, extended use should be limited to 8 hours. You can also consider discarding your PM2.5 filter immediately after you finish the task.

However, you should also consider hygienic and practical concerns to know when it’s time to dispose of the filter. As Smart Air India’s researchers tried to measure the lifespan of N95 masks, they found that filters’ usability does not just depend on saturation capacity. Its filtration efficiency can also be affected by the following factors:

Air resistance

Imagine a sink strainer that’s full of gunk. All those trapped food barely let water pass through, right? Likewise, filters that have already isolated much PM2.5 cannot facilitate proper airflow. Proper ventilation within your face mask and filters is vital for the process of adsorption to work.

Sign that it’s time to change your filter: It’s getting harder to breathe with the filter on. You might also notice discoloration, since filters nearing max capacity tend to turn grayish.


Over time, PM2.5 filters can get moist. Apart from that uncomfortable gross feeling, water can greatly reduce the electrostatic charge within the filter on which its layers’ filtration efficiency depends. 

Sign that it’s time to change your filter: The inside of your mask starts to feel wet.


Prolonged use can affect the structural integrity of PM2.5 filters. In previous paragraphs, we’ve discussed how poor facial fit can greatly reduce their efficacy. Folds, tears, and other manifestations of deformation limits the surface covered by the filters, allowing pollutants to get through your mask.

Sign that it’s time to change your filter: You’ve noticed that your filter developed folds, tears and other damages to its structural integrity.

Can PM2.5 filters be washed?

pm 2.5 filters airnex


You might be tempted to just wash your PM2.5 to save a few bucks, but doing so isn’t advisable.

Washing PM2.5 filter after the recommended period of extended use

Remember that PM2.5 filters work through the process of adsorption, not absorption. Separating the fine particles from its activated carbon layer through washing isn’t possible. Unlike absorbent items (e.g. reusable pollution masks, neoprene dust masks, etc.) which you can clean with hot water and soap, it makes no sense to wash this product. 

Washing PM2.5 filter in between intermittent use

Lab tests conducted by Smart Air warned that washing N95 masks with soap and water decreases its effectiveness by 21%. Likewise, using alcohol for disinfection can cause a 37% drop in filtration efficiency. 

Both N95 masks and PM2.5 filters are designed with layers of thin, randomly aligned fibers. Their electrostatic charge which facilitates the process of adsorption is removed when exposed to water and alcohol. Moreover, vigorous washing can cause damage to the filter’s structure. 

pm 2.5 filters airnex

Smart Air’s researches highlighted the use of UV Light as the safest method for quickly sanitizing masks before being reused. Contrary to water and alcohol, lab tests showed that it causes less than 2% decrease in filtration efficiency. Consider investing in a portable UV-C Light Sanitizer to disinfect your carbon filter in between intermittent use.



Bottomline, a PM2.5 filter can be used for as long as it has not yet reached its full carbon layer filtration capacity, which is prescribed by NIOSH to be around 200g.

The specific number of hours to fill up its activated carbon layer depends on how dust and polluted your environment is. Filters can last from 16 to 24 hours of ordinary use, but should be replaced within 8 hours when performing dusty activities.

Note that these recommended time periods are based on the capacity of high quality PM2.5 filters, so be sure to check if your purchased products are backed by certifications and lab tests.


PS. If you enjoyed this article check out the Airnex PM2.5 Activated Carbon Filters in our store!


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