What happens to the filtration efficiency of N95 masks after they are cleaned?

N95 masks are world-famous for the filtration quality that they provide to their users. During the pandemic, they proved to be a very effective part of the personal protective equipment PPE. With the rise in the coronavirus, the demands of the PPEs started increasing. The quality protection equipment was in full demand. Manufacturers around the world were busy in preparing the N95 masks and N95 respirators. 

The Center for Disease Control and Command (CDC) along with the National Institute for Occupational Safety and Health was busy finding ways to cope with the virus at home. However, the virus did not seem to be stopping and it continued to spread. The conditions became worst and people suffered each day. At this time when the crisis was reaching its peak, a shortage of N95 caused other problems.

Hospital facilities were left with an only limited stock of the N95 masks. People were also in search of the N95 respirators. It created further issues for the government. The retail stores and markets were flooded with fake N95 masks. These fake N95 masks did not protect the levels as provided by the NIOSH verified N95 masks. 

So, research institutes and other government departments started to find ways for the effective reuse of the already available N95 masks. Although the manufacturers did not say anything about the reuse of the N95 masks and initially the N95s were being used for the 1-time purpose. But the researches proved to be very effective and various ways were discovered to decontaminate and reuse these N95 masks. 

Methods to Clean and decontaminate the N95 Masks

Methods to clean the N95 masks from the contaminants and the germs were found. These methods were tested by the different authorities and then later on given the green signal for the use by the healthcare facilities and the general public. 

The following are some of the methods that were given the green signal for the cleaning and the reuse purposes of these N95s.

  • Boiling at the high temperatures:
  • Hydrogen Peroxide treatments:
  • Use of the UV Radiations:
  • Steam Treatments:

All of the methods were tested before their use officially. During the testing process, some important factors were kept in mind to ensure that the methods did not affect the filtration quality of the N95s. A proper guideline was prepared for the checking of various parts during the decontamination and the cleaning process.

If the cleaning process damages the seal and tight fit ability of the N95s, then the cleaning process is not good. Similarly, if the polymer fibers of the masks are destroyed at any step of the cleaning, the cleaning method cannot be used. The methods were checked for these features and then tested for at least three times. If at any step during the three times testing the N95s gets rough or shows any problems, the methods are harmful to the decontamination process. 

For instance, take the example of ethanol. It first experimented that ethanol spray can decontaminate N95 respirators without damaging any of its fiber or threads later, it was proved that ethanol spray destroys the threads on the N95 respirator. So this method is harmful to the decontamination process. This process of purification was later excluded from many white papers 

Filter efficiency after cleansing and decontamination:

The efficiency level of N95 respirators is not affected by the purification process if, the process is safe enough. The process mentioned in the article is the verified methods used for the purification process. These methods to purify N95 respirators are accepted by many doctors and firms including FDA. 

FDA has allowed the reuse of 3M N95 respirators after disinfecting it carefully. FDA's stance on this was appreciated by Mr. Alex Azar the health secretary of the United States of America. He has stated that the decision was taken responsibly by FDA. He encouraged the thought that N95 respirators should be reused.

After the purification process, the N95 respirator’s efficiency is not affected at any level. N95 respirators after purification are like newly manufactured N95 respirators. The filters as well as the breathing efficiency is not affected a bit.

N95 respirators can be purified up to two times maximum. When the masks are contaminated for the first time they should be disposed of if possible but if you are willing to reuse it. You must purify it using one of the four verified methods by the FDA and CDC.

When N95 respirators are cleansed for the first time the filters are new and can handle the process without being damaged and can be restored to its fullest extent and the same in the second time but a little lesser this time. This time the filters are less strong than the last time and are more delicate so there is a chance that they might get damaged if handled carelessly.

The third time is its end, this time while purification the filters are weakened and there is a definite chance that the filters will be damaged or the threads might come if resulting in the poor protection against germs and airborne dust and fluids.


Decontaminating N95 respirators is a nice start but it must be kept in mind that this requires care and complete focus, carelessness can lead you to many disastrous circumstances. The N95 respirator should be checked for damages after the purification and cleansing process as it might have been damaged.

Secondly, N95 respirators should only be used three times not more. The fourth time it is of no use and will provide almost no protection, breathing can become difficult. So it is better to dispose of it after three uses.

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