PM 2.5 Vs N95 Vs N99: What’s The Best Face Mask for Me?

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Hi there, this article is here for your information to understand how well these masks can do in protecting us from COVID-19, so you could choose what fits you best.

As some readers are a bit confused about the performance of ‘PM2.5 masks’, we believe it’d be better to explain specifically. Please go to Frequently Asked Questions for details.

We hope this article could protect you against scams and you don’t waste your money on something useless. But please keep in mind that even N95 masks could not 100% isolate you from the coronavirus, and wearing cloth face coverings is better than nothing.

umber of cases since the pandemic started for every 100,000 people
Number of cases since the pandemic started for every 100,000 people

The most susceptible groups are the elderly, those already suffering from a medical condition and folks lacking social safety net. Healthcare professionals have recommended several strategies to minimize the risk of contracting the virus. The most basic is to avoid panic. Fear does more harm than good.


Before looking at some of the ways you can prevent yourself and your loved ones from contracting the virus, it is prudent to first have a look at how it spreads. Human coronaviruses affect the lungs, throat, and nose. The viruses can be transmitted through any of the following means:

  • Respiration droplets produced upon sneezing or coughing
  • Close and extended personal contact like shaking hands or touching
  • Touching something containing the virus then using the same hands to touch areas of entry like the eyes, nose or mouth

We suggest you go through the article carefully, but if you’re in a hurry? The short answer is:

  • N95, N99, FFP1, and Surgical face mask(if wear properly) work.
  • PM 2.5 mask (cloth pocket with replaceable activated carbon filter inserts) may work at some level, but we don’t recommended it because of insufficient data.
  • N95 masks are tighter than surgical masks (loose fitting).
  • N95 masks aren’t tailored for kids or adults with facial hair
  • The mask is NOT reusable( And you can’t wash it with water or alcohol)
  • The mask lasts no more than 8 hours (If used continuously)
  • Don’t forget to wash your hands, it’s as important as wearing masks.
  • Air Purifier doesn’t work as you expected.
  • Cpap and portable oxygen concentrators are not therapy solutions nor are they considered to be some kind of cure. Although sometimes you need them
  • If N95 is sold out, or you’re in a limited budget, try KN95, you can get them from approved, CDC test report inside, fast delivery)
Mask protection level
Image Source: Masks For Heroes

Wearing Face Masks Can Protect You From Coronavirus?

Wearing the wrong mask or putting it on incorrectly does not offer protection at all. Therefore, you need to make the right decision when it comes to your choice of mask.

Another effective way of avoiding getting harmed by the tiny Coronaviruses either in the air or from a person is by wearing a mask. Masks are available in different specifications, brands, price tags, and types.

PM (particulate matter) 2.5 remains the longest within the atmosphere. This matter is responsible for plaque deposits in the arteries, lungs, throat, and nose. In the most severe cases, it can cause a heart attack.

Masks are more important to the infected folks. For the infected ones, they combat the transfer of drops related to respirational infections. For instance, when you wear a mask, you prevent yourself from coughing onto your hand, meaning even when you shake someone’s hands, chances of transferring the virus are minimized. Simply put, putting on a mask interrupts or halts transmission.

Can you use any mask? No! The most effective ones are biological grade types. While they are costlier than others, they do a good job of preventing transmission. One of the major drawbacks of the other masks, such as the surgical ones, is the fact that they become damp from your breathing. This means that if an infected person was to cough on them, it can really make matters worse.

Particulate respirators are handy when it comes to preventing the breathing of airborne particles. Currently, NIOSH has classified masks into three main groups:

  • P-series
  • R-series
  • N-series
  • K-series

Each of them boasts three unique efficiency possibilities – 100, 99 and 95.

N95 masks and medical surgical masks
Source: Masks For Heroes


N100, N99, and N95 are the three models of the N-series. These masks are not oil resistant. Because of this, they offer protection against both liquid and solid aerosol particles without oil. Common examples of non-oil based solid matter consist of ‘dust’ particles from non-oil-based liquids, pollen, wood, metal, flour, iron ore, and coal.

The N-series masks have been handy during the coronavirus pandemic. The N100, N99, and N95 constitute the N-series. The only difference among them is the efficiency level of their filter. The higher the rating, the more particulate matter the mask is able to filter out.

When it comes to coping with the Corovid-19, the most commonly used mask is the N95. One of the attributes you need to note about respirators in this series is that they lack a non-specific shelf life. What this means is that you can utilize them provided you do not damage them or there is no detection of breathing resistances.

N95 vs. N99

Note: The only difference between N95 and N99 respirators is the fact the former filters up to 95% of particulate matter while the latter blocks up to 99% of particulate matter.

Of all the masks, the WHO (World Health Organization) recommends a military-grade N95 mask as the most efficient and dependable for protecting against the stubborn Coronavirus. In addition to helping block viruses and bacteria, these masks also protect users from inhaling the tiniest of particles.

A great highlight about these masks is that they firmly fit your face, unlike others. On top of blocking tiny particles, they are also efficient anti-pollution dust respirators. They feature the science of layering and biotechnology combines to guarantee the utmost standard protection.

Some masks on this series feature valves that are handy for air exhalation. With the valves, the last thing you have to be worried about is moisture accumulation close to your eyes or nose bridge.

The N95 respirator stands out as the most popular among the 7 types of face masks for particulate filtering. The NIOSH has approved certain products to act as N95 masks. The FDA has also cleared the same products as surgical masks. They go by the name Surgical N95 masks.

Note: Find the list of the NIOSH-approved N95 masks here(From CDC). For a more comprehensive table of the products, click here(From CDC).

N95 and N99 masks for coronavirus come in an array of styles, shapes, and colors. Some brands and styles fit users better compared to others. Some shapes or styles are more comfortable. Provided your desired mask is NIOSH-approved and meets all the OSHA requirements, you are good to go. It should be able to protect you against the virus in spite of style, shape or color.

How to wear a N95 respirator correctly
Source: Masks For Heroes


P100 and P95 are the two models of the P-series. These masks are almost the same as the R-series ones. For starters, they are oil resistant meaning they offer protection against liquid and solid aerosol oil-containing particulates. The only difference with the R-series is that these boast a longer service life. NIOSH recommends their disposal to be after a month or 40 hours of use.


R95 is the only model of the R-series. These masks are oil resistant. As a result, they offer protection against liquid and solid aerosol oil-containing particulates. NIOSH certifies its use for only 8 hours. Because of these restrictions, they are the least commonly used.


K-series is a standard commonly applied in Asia. KN95 and KF94 are Korea and China standards respectively. The KN95 respirator is the equivalent of the European FFP2 and American N95. This means that it filters up to 95% of particulate matter with a 0.3 micrometers diameter. The mask can offer protection from PM 2.5, PM10, and even tinier particles.

KN95 boasts a state-of-the-art carbon filtration tech coupled with an improved electrostatic microfiber to offer protection against any of the following:

  • Smog
  • Germs and bacteria
  • Pollen
  • Fragrance and odor
  • Animal allergens
  • Automobile smoke and exhaust

Note: The FDA has certified KF94 as capable of blocking PM 2.5. It is also handy at blocking the entrance of germs and viruses. Just like their name suggests, they can block particles up to 94%.

Frequently Asked Questions

Coronavirus 2019-nCoV disease prevention
Source: Masks For Heroes

Q: How is N95 different from other masks (read facemasks or surgical masks)?

Well, many factors inform the difference between a surgical mask and an N95 mask. The latter basically minimizes your exposure to tiny, airborne particles. It could be the larger droplets or smaller particle aerosols.  N95 masks are tighter than surgical masks. Facemasks feature loose-fitting hence making them inappropriate to wear particularly when visiting high-risk areas. However, when in low-risk areas, you can wear them.

Not everyone can put the N95 respirators. This is especially true for those with breathing or respiratory issues.

The main use of facemasks or surgical masks is for source control. A person with a confirmed/suspected coronavirus case ought to put on a mask until he or she is secluded at home or in a medical facility. Once he or she has been quarantined, there is no need to wear a mask.

Q: Is PM 2.5 mask recommended for COVID-19?

PM 2.5 particles are a sophisticated combination of different pollutants. The highly tiny particles can be lodged easily into your body. While PM 2.5 masks can be effective at preventing other things such as mist, and smoke, they are not ideal for protection against COVID-19.

Note:  We can see from the illustration below that coronavirus (SARS-CoV-2) is much smaller than PM2.5, plus we don’t have any solid evidence as to how efficient PM2.5 masks are in protecting us from COVID-19.

Comparison Particulate matter vs virus

On the contrary, we do have known the filtration efficiency of home-made cloth masks (~69.4%), surgical masks (~80%), and N95 respirators (~95%). So, instead of “recommending” something without support of data, we do believe it’s better and safe to be conservative.

It’s not that PM2.5 mask is totally useless, we just don’t have sufficient data to draw a definite conclusion. That’s why we can’t and won’t “recommend” it unless reliable, experiment-based data become available.

Again, N95 masks provide the most safety margin and they’re a must for healthcare workers; cloth masks and surgical masks are enough for ordinary people in sparsely populated areas.

Q: Air Purifiers Work For COVID-19?

The virus responsible for COVID-19 is roughly 125 nanometers or 0.125 microns in diameter. Many people are wondering whether air filters featuring HEPA filtration can capture the virus effectively. The size of the virus falls within the size range that HEPA filters seize with remarkable efficiency. According to this NASA study, HEPA filters are effective at capturing the tiniest of particles meaning they can help remedy the situation.

Air purifiers, although an expensive alternative to other protective methods such as the use of masks are great at not only containing the virus, but also other things such as odors, chemicals, microorganisms, and bacteria. Having said that, this does not mean that you are of utmost safety when using an air purifier. As scientists and researchers continue to research about the coronavirus, it is important to do your part and exercise caution.

Q: Should I put on a mask in public?

A: According to evidence, some people are asymptomatic, meaning that they are carriers of infectious coronavirus and can spread the virus for sure, but they don’t have noticeable typical symptoms of COVID-19.

If you happened to be around anyone of them, your risk of contracting the virus is pretty high if you are not wearing any protection gear.

Wearing a mask, therefore, is an effective way to keep this nasty virus away.

Some of the preventive measures the CDC recommends include avoiding touching nose and eyes before washing (with soap) or sanitizing your hands, keeping off close contact with a patient confirmed of the virus, and always covering your sneeze or cough using a tissue.

For unlucky sick ones, please avoid mingling with the public or visiting people in hospitals. It is prudent to quarantine yourself by staying indoors.

Q: I’m visiting a high-risk area, what do I need to wear?

A: If you are visiting a high-risk area such as an airport or hospital, you MUST put on the N95 mask coupled with goggles.

Q: I suspect I have COVID-19, what gown, mask or protective gear should I use?

A: If you are a patient with confirmed or suspected COVID-19, you need to put on disposable and nonsterile patient isolation gown. This protective gear is often handy for routine patient care within the healthcare setting.

Q: Any difference between coveralls and gowns?

A: Gowns, unlike coveralls, are more effortless to take off and put on. Coveralls offer 360-degree protection as they are tailored to protect the entire body, from the lower legs to back, feet and head. Isolation/surgical gowns do not offer the entire body protection., as they feature openings at the back. In most instances, they cover the mid-section part only.

The other difference between the two has to do with heat stress generated. Gowns generate less heat stress in comparison to coveralls because of several factors. Chief among the factors is that their design has an opening coupled with its fabric material.

Q: I recently traveled from a high-risk region. What do I need to do?

A: If you traveled to high-risk countries such as Iran, Italy or parts of China within the last two weeks, you should restrict contact with people for up to two weeks. Remaining at home and self-isolation helps minimize risk by a huge percentage. Contact the relevant authorities or government departments within twenty-four hours of arrival for guidance.

In the unfortunate event that you fall sick, these steps should be handy:

  • Check yourself into the nearest medical facility
  • Self-isolate
  • Wear a mask
  • Keep off close contact with individuals in long-term care centers and hospitals, particularly senior citizens as well as those with delicate immune systems or chronic conditions
  • Keep your visitors off your home
  • Always cover your nose and mouth with your arm (dubbing style) when sneezing and coughing
  • Rather than running errands, opt to have supplies delivered. The delivery guy needs to drop off 2-meters from where you are

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103 thoughts on “PM 2.5 Vs N95 Vs N99: What’s The Best Face Mask for Me?”

  1. Hi. Thank you for this article. I recently purchased a Base Camp reusable N99 mask with replaceable active carbon filters. It also says M and pm2.5 on the side of the package.
    Did I just waste my money?

    Regards and thank you

    • Basically, Base Camp N99 is to protect you from air pollutions, but it has limited performance of virus filtration. However, you can still wear it as a protection. It’s better than nothing.
      Just stay away from ‘hot spots’ or crowded places if you have to go out for essentials.
      Also, keep in mind that you have to wash your hands with sanitizer gel or soap before changing the replacement filter.

  2. So based on this article a mask that has a replaceable PM 2.5 filter is useless against coronavirus. But CDC is telling people how to make a mask using a bandanna or from regular cloth, how can this be better than a mask made from cloth with a filer that has charcoal?

    • John, thanks for your question and we’re more than happy to explain a bit. First, the CDC gives its advice on a severe shortage of medical products. They hope to stop or at least reduce the spread in a way that most of us, the public, find easily and works to some extent.

      While cloth and bandana are available to basically everyone, masks with activated charcoal filters are nowhere to buy for many.

      Moreover, given the size of coronavirus (65–125 nm in diameter), smaller than PM2.5 particles, it’s hard to keep all viruses out. Since the filtration efficiency of cloth and bandana face coverings can reach 80%, which is fairly enough for us, but still not a 100% guarantee.

      That’s why CDC ALSO STRONGLY suggests staying home as much as possible, 6ft person-to-person distance, and frequent hand-washing.

      At last, as we are fighting against a novel virus, there are things that scientists don’t know, and we believe CDC guidelines will be updated in the days to come.

      • My question which is the best mask to wear? A plain bandanna, DYI mask from cloth or a mask made with cloth that can use PM2.5 fitlers? I know right now to purchase any mask that is N95 and hopefully it is N95 because the market is being flooded with non N95 mask. Which one of the three is the best based on CDC guidelines.

        • Too many complaints from people who are buying from banggood. Please research more reputable places to send people to! Stick to sleep advice and not medical supply advice!

          • Earlier days we don’t have a choice, Amazon Walmart and Homedepost are all out of stock.

      • Let me ask John’s question in a different way. Do cloth masks with replaceable PM 2.5 carbon filter’s work better against corona virus than bandana/scarfs, etc.?

        • As outside air may flow into the cloth mask through gaps around PM2.5 carbon filters, it’s performance would not be much better than just bandana/scarfs. Wear bandana/scarfs, or cloth pocket with PM2.5 filters only when you couldn’t get those 3M PM2.5 masks, surgical masks or N95 respirators.

        • Hello Terry,

          What do you think about these masks. Some are sold out but the ones towards the bottom have 3 layers and have a copper layer in the middle, which is supposed to be effective against viruses. It also has a copper carrying case 😂

          Let me know if you think these would be worth buying or if I should just stick with the cheaper surgical masks. Also, are the surgical masks good for only a single use?

          The link to the copper masks are below:

          • Hi Miles. Thanks for sharing. Neither have I found any information as to if the mask protects against covid-19, nor its filtration performance like N95/KN95/KF94.

      • the size of the virus is irrelevent as it is not present singly and cannot move! It exists only in aerosol droplets. Which are far bigger typically 1-5nm for treue aerosols and way bigger for droplets and aggregate due to surface tension on the outside of a mask . As it is believed that catchng CV19 and severity of disease are dependent on exposure period hence dose then a PM2.5 multilayer mask will ba way better than a cloth mask. Also KN95 or N95 are considered as effective largely against CV19 and they only filter down to 2.5 microns. Even an N99 won’t keep out all bioaerosol particles ! So distance plus reducing time with other people plus a pm2.5, PN95, n95 mask should give the best protection . Distance and time being the main factors BUT if bioaerosols DO transmit CV19 then even 10m will not stop infection! One is therefore relying on dilution and airflow ..

        • Hi Mike,
          Let’s talk about some facts
          1. As I know, almost everyone in Eastern Asian countries (Japan, China, Korea, etc) wear onetime surgical masks, and we all know the result, it works.
          2. No pm 2.5 filter inserts brands mentioned that they can protect you against coronavirus, they are designed for woodworking, cycling, hiking.
          If you think it MAY work, just do what you want, it’s your choice. But you shouldn’t recommend other people using it as well. At least I won’t do that on my site.

        • Mike … You are bang on. the PM 2.5 mask is far superior to other cloth masks, surgical masks, etc. Just not the N95,

          ” It’s not that PM2.5 mask is totally useless, we just don’t have sufficient data to draw a definite conclusion. That’s why we can’t and won’t “recommend” it unless reliable, experiment-based data become available.”
          — Terry Cralle

          The most recent research is demonstrating that the SARS-CoV-2 virus is capable of being “aerosolised” or transmitted through aerosol as its mode of “transportation”.

          The PM 2.5 mask is effective at levels where particulate matter (aerosols) can be as small as 2.5 microns or micrometers. While we know that the SARS-CoV-2 virus is approximately 0.2 microns or micrometers in diameter, it, by itself can slip through a PM 2.5 mask.

          The key that you identified Mike is that the virus does not get transmitted by itself and relies on a vehicle for transmission. As much of the prevalent thought is that it is transmitted mostly by way of fomites and droplets from couching or sneezing, it has overlooked, until recently, the aerosol mode of transmission.

          Of course, other points here are correct too … the mask is only as good as its fit. The surgical mask has large openings on the sides. The N95 masks are “form fitting”, so they reduce the capability of outside air from being inhaled unless it is filtered through the mask.

          A good PM 2.5 mask is the same.

          A good form fitting mask will be more superior than the other style of masks. The keys though, is to treat it like a single use mask … meaning it should be washed/cleaned after every use and to have extras on hand for rotation that permits cleaning of one mask while the other is being used.

          As noted here though, another key is the effectiveness of the carbon filter and its efficacy over time and at what point they should be replaced. The thought is that it should be replaced much sooner than you think.

          A good summary is:

      • An PM 2.5 is far superior to most woven cloth/homemade solutions and superior to a surgical mask when the pm2.5 provides a tight seal.

        Surgical masks are typically three ply/non-woven, however even when properly worn air gaps are left on the sides in the pleats. Should somone sneeze within 17 feet of you and you breath in at the same time, you have the possibility of bypassing the filter on a properly worn surgical mask due to their design, by breathing the droplets in through the gaps on the side.

        Surgical masks are meant to prevent the Doctor or Nurse from infecting the patient, not necessarily the other way around. That’s why they have now upgraded to N95 so that transmission is stopped I’m both directions in medical settings during this pandemic.

        PM2.5 come in several varieties so do your homework. The flat strip do not protect as well as the triangular pocket style, However so long as there is a tight seal, it will provide better coverage than a surgical mask by only allowing 10micron. This virus is not aerosolized. A cough can only travel around 6 feet (hence social distancing), but a sneeze is just shy of 20 ft!).Most woven cloth can even defeat 10 micron hence why they are better than nothing, but the key for us regular non-front line individuals are multi layer solutions with a good seal. This is why you typically see medical personnel with a mask and a clear shield = layers.

        Any mask is better than no mask, but it is not a substitute for practicing social distancing, leaning hands and surfaces regularly, and taking safe precautions to limit exposure whenever possible.

        This is not legal or medical advice and is only my opinion. Please do your own due dilligence.

        • Best advice ever. This debate is almost like Regular gas vs Premium gas…. However, if my car says Premium, that’s what I’m going to use. Mask wearing, with or without filters of any kind or facial coverings; I’m going to err on the side of caution!

          • The theory that SARS-COV-2 is carried by aerosols is still under scientific evaluation, as stated by the WHO (in their 9th July 2020 scientific brief about Transmission of SARS-CoV-2).
            Current studies, that have been conducted under laboratory conditions, show that we still need more insight regarding the infectious aerosols generation and transmission.

            So far, studies conducted in health care settings where COVID-19 patients were treated report the presence of the virus in air samples, while other studies show NO presence of the virus in air samples. However, some outbreak reports related to indoor crowded spaces (outside medical facilities) show the possibility of aerosol transmission (combined with droplet transmission). Still, there needs to be more research that is not only conducted in laboratory conditions, and that is conducted in various settings and situations. Until then, we are required to wear masks as a part of the protective measure as recommended by the WHO.

    • Jeffrey, as we mentioned in
      “CPAP machine and (portable) oxygen concentrator manufacturers have stated in the wake of the coronavirus outbreak that these devices can provide potential care to the infected patients. Since respiratory failure is the main problem with the coronavirus infection, units like CPAP machines and oxygen concentrators can provide therapy and continuum of care as well as help with the COVID-19 therapy response.

      It is important to point out that these units are not therapy solutions nor are they considered to be some kind of cure. Infected patients are primarily in need of medical respirators or ventilators, and units like oxygen concentrators or CPAP machines can provide temporary relief. Moreover, such use of these units is not FDA approved, because the standard framework for respiratory support relies only on respirators or ventilators.”

  3. I read the previous replies about the effectiveness of the pm 2.5 masks vs the homemade masks and bandannas. I’m still confused. Is the the pm2.5 mask more or less effective? Yes or no. What percent could this type of mask filter?

    • To our best knowledge, there’s no solid evidence as to the exact filtration efficiency of COVID-19 by pm2.5 masks and home-made face coverings. So, we could only assume that pm2.5 masks may do a better job than cloth face coverings. But we are sure that their performance is way below N95, KN95 or the like.

      For most people, It’s meaningless to talk about pm2.5 or something similar. Search in Google for ‘n95 mask for sale’ or ‘kn95 mask for sale’, if you want to protect yourself and your family.

  4. Wrapping a piece of cloth around your face is going to be less effective than a piece of cloth with at least a PM 2.5 carbon filter in it. There’s at least going to be some protection there. Surgical masks have a terrible fit and obviously real N95 makes are hard to come by. I would rather have a tight fitting cotton mask with some kind of filter in it, than just a scarf or nothing at all. No mask is going to protect you fully from the virus particles but to suggest any filter is useless doesn’t make sense.

    • Totally agree with you. The author of this article for *some reasons* avoided directly answering the questions if a mask with PM 2.5 filter is more or less effective than a handmade mask. And it’s bullshit to say a surgical mask works (and better than a mask with PM 2.5 filter)

    • I totally agree, Elaine.
      This entire Q&A section is very confusing as some answers contradict previous responses. Consult official research, epidemiology and microbiology websites for more precise information.

      • Hi Dina. I’ve updated the FQA section to make it less confusing. Also, will continue to update the post as new information/evidences come available. You’re totally right that we should all absorb information from multiple resources.

    • That’s like saying a colander can be good for holding water. The virus is so small it goes right past the filter just like water pouring through a colander.

  5. Useful info. Fortunate me I found your web site by chance, and I’m stunned why this coincidence did not took
    place earlier! I bookmarked it.

  6. i ordered cloth masks with PM2.5 inserts. I’ve also ordered surgical type masks, all from China.
    I have some reservation about the safety of the PM2.5 inserts and the surgical masks. What I’ve been doing is putting a trimmed surgical mask inside the pocket of the cloth mask. I’ve also been adding a piece of t-shirt to the inside of the surgical mask, so as not to breathe any fibers that may be on the mask.I have not used a PM2.5 insert yet, too nervous.

    Am I overreacting? Should I not go to such lengths? I understand that if any of those coverings had any virus, the virus would not live long enough to make the trip from China. Right?

    Also, like with some home made vaccum cleaner bag masks, would I have to worry about breathing any fibers with either one? I don’t want to keep wasting any more surgical masks by substituting the PM2.5 filters with them.


    • Hi Anthony. Virus won’t last that long trip from China. And, wearing a quality surgical mask is enough for us in sparsely populated areas, as we are not in close contact with a crowd of infected patients.

      To stay away from breathing difficulty in hot days, you could wear an N95, or put a surgical mask outside your PM2.5 cloth mask, if you have to access highly risky and packed areas like hospitals.

      As to home-made vacuum cleaner bag masks, we don’t recommend using vacuum cleaner bags since you’ve got real masks.

      Don’t forget to practice social distancing, and wash/sanitize your hands before touching your face, eyes and mouth.

      • Just read – vacuum HEPA bags have glass paticles that could enter your lungs. Seems best to stay away from those.

        • Hi Duba, to our best knowledge, there are vacuum HEPA bags made with or without glass fibers. But we don’t know exactly which brands or manufacturers have added glass fibers into their products. So, yeah, best to stay away if not sure about the bag material.

      • What about:
        – wear surgical mask inside, then wear a PM2.5 clothing mask outside to fix the loose issue with surgical mask
        – wear PM2.5 clothing mask with a pocket, and use the surgical mask as a filter to the clothing mask
        Surgical masks and reusable pocket filters are readily available!

    • Anthony: I, like you , also purchased a mask with 2.5PM insert. What I used is my house AC filters, 3M filtrate 1900 series filters, where I gently removed the metal wiring and cut them down to size of the PM 2.5 insert and double layered them with scotch tape at 4 corners edges (to allow the pleats to bend into shape). 1900 series is near top of the line residential AC filter offered by 3M, which I trust. The 1900 series filters ~93% of virus and bacteria… double layer will bring that capture rate to about 99.5% with minimal impact to pressure drop. Just to be safe I followed the direction arrow of air flow specified on the filter by 3M (I assume is NOT directional but just to be safe). Of course I have the similar concern if it release any particulates…. You can always add your t-shirt layer on the side closest to your face. One comment, although cover-19 virus size is ~0.125 um, it is believed its dominant transport mechanism is through aerosol (moist breath) which those aerosols are on the order of 5 to 10 um in size. Of course, latest repot had mentioned virus can live ~ 1 wk… so I will make enough of these inserts to rotate them out in 3 week rotation so they will sit around for two weeks1 additional week guard band to allow the virus to naturally degrade. For my clothe mask, after wash and air dried. I place them on my car’s dashboard out on the drive way as surface temperature of the dashboard can reach between 150F (grey color dash) to 190F (black color dash). The high temperature and broadband UV natural sun light will for sure kill anything. I rotate 180 degree of the masks on the dash to ensure all shaded areas are exposed to sun light……. Stay safe. We will get through this and come out stronger.

  7. Terry, thank you so much for all of this information. You are very thorough. I work in healthcare. I am wondering about your thoughts on a mask from Keyparent called

    N95 Activated Carbon Face Mask respirator Mask for Covid 19 protection. Has 5 layers

    • Hi Lee, that site looks good, but you know, personally I won’t buy there, it’s a new site and sell almost everything.
      As I mentioned before, I prefer buying from sites that I trust, especially personal protective equipment.

  8. Why does the intro say the N95 is not reusable? I know it’s not designed to be reusable, but it is being reused with effective cleaning recommendations (steam or 160 degrees for 30 min, or waiting a week to reuse, etc)

    • Hi Kathy, we pointed out that N95 is not reusable simply because it’s not designed to be reuseable. You could find guidelines for reuse only because of serious shortage of masks/respirators these days.

      Also, it’s not a good idea to disinfect your mask with steam or high temperature. Leaving your mask in a dry, well-ventilated place is considered acceptable and recommended by CDC.

      • Thank you. What about the research that shows 158 degrees F for 30 minutes is effective for disinfecting & does not harm masks?

        • Hi Laura, we don’t recommend sanitizing masks with uv bottle sanitizers. Most uv sanitizers kill bacteria or virus with uvc light, which harms mask materials as well.

  9. Hi Terry: Thank you for this informative article. The surgical masks that have become available lately, whether it’s the pharmacy or hardware store, state they are non-medical. They look like the typical trifold blue masks (although some come in other colors). They don’t have a tight fit around the face but I don’t think the medical grade ones fit tightly either? Are they the “surgical masks” that you refer to in this article? And are they more effective than a cloth mask with pm2.5 filter?

    • Hey Helen. You’re right. Medical grade masks, i.e. the ‘surgical masks’ we referred to in this article, do not seal on our face like N95 ones do; but they are more effective than a cloth mask with pm2.5 filter.

  10. Hi,
    Why are you (and CDC) are saying N95 are not re-usable? If I use UV-C desinfecting bulb, or just leave N95 unused for a few days, is there any reason it won’t work again?

    • Hey Lazar. Simply because N95 masks are not designed to be reusable. CDC published reuse guidelines only because there was a shortage of mask supplies, where we have to compromise between slightly reduced safety margin and having nothing to use. While the uvc bulb is not recommended, leaving your N95 in a dry, clean and breathable container is acceptable in order to ‘reuse’ it.

  11. What are the specifications for a “surgical mask?” There are dozens of options for them available on Amazon, for instance. How do you know which ones to buy?

    • Hi Tracy. Amazon is a credible online market. It only let in legal and qualified sellers. No need to worry too much about ‘surgical specifications’ as Amazon has ensured the standards of product quality.

    • Hi Dr Richard McCabe. Thanks for sharing another solid evidence that N95 rated masks do protect us from some virus and PM2.5 pollutants. However, it seems that the report does not mention anything about PM 2.5 filter.

  12. I have a washable cloth mask with a PM 2.5 filter. While I know that I can wash and re-use the mask, how often can I re-use the filter? It seems that if if I re-used the filter in a washed mask, the filter would immediately contaminate the mask. Please advise.

  13. N95 is the certification level of American respirators, certified by the National Institute of Occupational Safety and Health (NIOSH). This type of mask can filter out more than 95% of non-oily particulate matter (aerosol) under the specified air flow (85L / min), so it is named N95. If it can filter more than 99% of particulate matter (aerosol), it is called N99 mask. In addition, corresponding to N95, KN95 Mask Mask is a mask certified by China’s GB2626-2006 Respiratory Protection Products Self-Suction Filtering Anti-Particle Respirator Standard. KN95 and N95 masks have the same protection level, but only follow the test standards of different countries. KN95 masks follow Chinese standards, and N95 masks follow American standards, both of which have a protection efficiency of not less than 95% for non-oily particulates (sodium chloride particulates for experiments).

  14. The masks you linked through clinical supplies are NOT USA they are CHINESE CHINA 🇨🇳 company with certificates
    NOT GOOD mascarading as USA

    • Hi Gm, I linked to clinical supplies because recommended it and people can buy some N95 masks there, although quite expensive. I have no idea if its masquerading as USA. If you are looking for other quality mask products, please also check out links directing to Amazon, Walmart, list of NIOSH-approved N95 masks or a more comprehensive table of the products. Oh, I’d be glad to replace the link if you have better options to share.

    • They uh… are made in the USA. You can verify their 3M NIOSH approved products on the website. Their KN95 masks can’t be made in the US because they are inherently Chinese, but I spoke on the phone (with hudson i think) and walked it through. You can validate against batch numbers etc…

  15. Hi Terry, thank you for the useful summary of all the different standards. Two questions…

    I’ve been using KN95 for any activity indoors and a cloth mask for social responsibility when just walking around outside where other people are. Do you see any incremental benefit to adding one of the PM2.5 filters into a cloth mask? Are the inserts made of melt-blown polypropylene?

    Regarding the safety of UV-C on respirators, do you remember the source that said it wasn’t safe for the masks? I kind of went down the UV-C rabbit hole and built a sanitizer using this study as “validation”

    • Brian, Hi. Thanks for your kind words and I’m glad to help. As far as I know, most PM2.5 filters are filled with activated carbon and some have non-woven inside. Better confirm with the seller. Inserting a PM2.5 filter into a cloth mask has limited ‘incremental benefit’ as compared to wearing a cloth mask without it, if you are thinking about keep outside the corona.

      The study you mentioned is the source I referred to. I think this study has provided solid evidence that uvc is not an option for disinfecting masks.

    • Hi Stephanie. The mask you referred to looks identical to this one on Amazon. It works just like any other cloth masks with filter inserts. Wear it only when you couldn’t get 3M PM2.5 masks, surgical masks or N95 respirators.

  16. Hi Terry,
    Thank you for this useful post of mask information. It was very helpful.

    I just purchased a couple KN95 masks to try out from the local medical supply store and it says “PM2.5 – National standard – GB2625-2006 KN95 and the company name “Sky Screen” on the packaging.”

    I’m immune compromised due to autoimmune medication I take, my husband is not but works with the public.

    Would this KN95 PM 2.5 mask be something I can trust for best protection against coronavirus, or should I stick with the 3M N95 masks I had from our house demolition, and he be protected ok with these KN95 masks for his work day?

    Also, was curious what is the recommendation for how often these masks be thrown out and a new one be worn? Maybe I should have 2 that I rotate if I’m in a store with a lot of people where viral particles could be in the air? Would wearing them a few months be a bad idea if I’m rarely in public but need to do a grocery store run every 2 weeks?

    Thank you in advance.

    • Hi Kelly. Glad to help. Are you sure that the national standard you saw on its packaging is “GB2625”? If yes, I seriously doubt about its quality because thats not the standard for masks. KN95 masks should be made as per “GB2626” to have equivalent performance with 3M N95.

      If you have genuine KN95 masks, they will protect you and your husband in public settings.

      As to when to throw away the old mask, I personally count hours of use and change at the end of its service life as specified.

      • oh! that was a typo. it does say “GB2626”! my main concern is that I’m wondering if the KN95 masks w the PM2.5 on them would be protective against coronavirus particles. Seems these would only help against pollutants? thank u for your time.

  17. Hi Terry, my job is returning to in person and I am trying to purchase masks I can use that will protect me. Can you post a list of reputable websites to purchase from? It would be very helpful.

    • Hi Cathy. I truly appreciate your trust in me but I can’t do this. The investigation required is beyond me. Making this list is such a challenging task even for CDC. The good news is they’ve published a list of approved N95 mask manufacturers.

      Speaking of N95 masks, they’re necessary only for those working on the frontline. We could buy some KN95 or equivalent ones on Amazon or Walmart because products of poor quality have been kicked out of their lists.

  18. I am really happy to say it’s an interesting post to read.
    I learn new information from your article, you do a excellent job.

    Best regards,
    Lunding Dencker

  19. You posted a comparison chart that did not include KN95 masks. Can we please have the percentages for virus, bacteria, dust and pollen for these masks? Thank you!

  20. I am considering buying a level 2 surgical mask: MASK, ASTM LEVEL 2, EARLOOPS, BLUE – 50EA/BX, 40BX/CS FMT605 from ASP Global. Is this going to be better than a level 1 mask? Will it be harder to breathe through? It is going to be worn with a face shield.

    • Hi Barbara. Technically, ASTM level 2 masks are better than level 1 ones. You won’t have much breathing difficulty when wearing a surgical mask. Putting on a face shield also raise the level of protection.

  21. Great site with lots of useful information on COVID-19, transmission, and various masks.
    I have several N95 masks and I have started to purchase re-usable cloth masks with the 2.5PM inserts. I recently saw an ad for a mask featuring a 0.3PM insert. Have you heard of this insert?
    Would the 0.3PM insert filter smaller particles than 2.5PM or am I reading something into it? Thanks again!

  22. KN95 masks that are supposedly NOT reusable…. I use a mask when I go out to the bank, shopping, etc. Most of the time, it is only used for 15-45 minutes.
    It seems to me that when they recommend a 1-time use, they are talking about people wearing it all day. True?
    If I am using for such a short time, and then using another KN95 mask for the next time (rotating them and letting each mask sit for 4 days or so) – it seems that I can safely re-use each mask multiple times since each mask’s useable time is still low.
    Is there anything faulty in my logic?

    • Hi Nancy. Their recommendation of 1-time use depends on manufacturer’s instructions and conditions of use. If you want to reuse your KN95 masks, please check out this NIOSH guidance for N95 respirators because KN95 and N95 are made as per equivalent manufacturing standards.

  23. I would like to inform you that you can buy Powecom KN95 from that are authorized by the FDA on appendix A at . You can purchase 50 masks for a little over a hundred dollars. The Powecom mask is rated over 99% by the NPPTL.

    • Hi Jeffrey! thank you for posting about our company ! We are so proud to be able to bring the FDA Authorized Powecom KN95 Respirator Mask to our customers.
      It’s great to have people like Terry helping guide people 🙂

      Just a little bit about us ….We are a family owned business and have been since 1938 and our parent company (Ball Chain Mfg.) is the world’s largest manufacturer of ball chains ( that you see on military dog tags, ceiling fans, handbags, light pulls, etc.. We make several million feet per week (all of the ball chains are Made in the USA). Our company started in a small garage in the Bronx, NY by my great grandfather and his son (my grandfather). We provide all the ball chains for the military and we take tremendous pride in everything we do.

      You will not find a more reliable, trustworthy company for the masks! We are very committed to bringing our authentic masks to everyone that may need them!

  24. Such a great article! My family and I enjoy outdoor activities such as bicycling and hiking. In our area we have had numerous wildfires. In rural areas the is not much concern about CV-19 especially when social distancing is properly practiced.
    Do you know how effective the carbon filter masks are at filtering out the harmful components of wildfire smoke?

  25. Hi there! thank you so much for your article.
    Could you tell me where can I get the authentic N95 masks? I looked at them on Amazon but a lot of people said that they bought fake N95 masks on this.


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