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Respirator Frequently Asked Questions

There are a lot of questions that I receive regularly regarding respirators and in this article, I thought that I would try answering some of them.

Some of these questions are ones that I receive regularly, some of them I’ve seen asked online, and some of them I have asked myself in the past!

With all of that being said, I hope that this post will help answer some of your questions about respirators and masks. If you have a question that isn’t on this list, I would love to know so that I can add it in the future!

This post contains affiliate links. For more information, please refer to my affiliate disclaimer

Information on this blog is for informational purposes only. Readers are encouraged to confirm the information herein with other sources. Furthermore, this information is not intended to replace medical advice from professionals. This website assumes no responsibility for the accuracy of the information, which is subject to change without notice.

N99 reusable respiratorsCambridge Mask N99 (Please note that this mask does NOT hold an N99 rating. However, it does meet N99 filtration criteria) | Cambridge Mask (Ebay)

What Are N95 Masks Used For?

Respirators, such as N95 respirators approved by the NIOSH have a variety of different purposes. Their overall purpose is to filter fine particles down, and often smaller than, 0.3 microns (0.3 micrometers) in size.

This means that they have a variety of different purposes. They are often used in medical settings to protect against viral and bacterial particles, and they are often used to protect against fine dust particles (air pollution).

Some respirators (such as R and P rated variants) are also effective against VOCs and airborne chemicals.

jonathan j castellon 74a0JAn2llQ unsplash

3M N95 8210 Respirator. You can purchase these N95 respirators on Amazon or Ebay.

Is KN95 the Same as N95?

No, a KN95 respirator is different from an N95 respirator. N95 respirators are rated by the U.S NIOSH, whereas KN95 respirators are rated by the Standardization Administration of China. That is to say, the N95 standard is U.S based, while the KN95 standard is based in China.

However, in use, these standards are very similar. In fact, they are almost identical. Recently, though, many KN95 respirators have been found to not meet the quality standards that they should (CDC).

KN95 Fine Dust Respirator

A KN95 respirator from China.

Purchase KN95 respiratorsKN95 Respirator | KN95 Mask | Amazon KN95

How Long Do N95 Masks Last?

Respirators are only rated to achieve their specified rating (N95, N99, etc) for 8 hours (CDC). Although they are only rated for 8 hours of use, there are a few factors that will influence lifespan. 

When used for viruses, respirators are best replaced after each use. Since viruses are easily transferred, it’s easy to contaminate the inside of the respirator and it’s better to replace them after every use.

If a respirator gets damp, it should be replaced straight away. Further, when using a respirator for fine dust, once breathing becomes difficult, the respirator should be replaced.
Respirators should not be used for longer than 8 hours in medical situations. However, when it comes to fine dust and air pollution there is no specified maximum life-span.

For the best filtration, replace respirators after 8 hours. However, when it comes to fine dust particles and air pollution, it is possible to reuse respirators for a few days or until breathing becomes difficult. 

Just keep in mind that respirators will lose effectiveness the longer that they are used. 

What Does N95 Mean? What About N99?

NIOSH (N) rated masks are some of the most common that are found. Although there are other ratings, the most common masks to find are N rated masks.

But what does N95 actually mean? Luckily, it’s pretty simple! The letter N signifies that a respirator is not oil resistant (R rated masks are oil-resistant and P are strongly oil resistant).

The number after the N signifies the filtration capabilities of the mask for particles of 0.3 microns in diameter. In other words, an N99 mask will filter AT LEAST 99% of 0.3 diameter microns. N95 will filter 95% and N100 will filter 99.97%. 

It’s important to note that the N rating is what the worst mask in the tested batch filtered at. This means that often masks will filter better than their rating. Further, although masks are rated to filter 0.3-micron particles, they often can filter smaller particles also.

Which Rating Is Best?

The most confusing part about respirators are the many different rating systems. From N to R to P, to KF to KN to FFP, there are a lot of different ratings! But what do they all mean?

I recently wrote a whole article comparing the differences between respirator ratings, and I recommend that you refer to that for more details. 

Generally though, the different ratings are due to different regional systems. Most of the world uses the NIOSH system, which rates masks as N (not oil resistant), R (somewhat oil resistant) and P (oil resistant). 

However, there are also KF ratings (Korean), KN ratings (Chinese), P ratings (Australian & NZ), D ratings (Japanese) and FFP ratings (European). Nearly all of these ratings have similar requirements, and there are comparable masks in all systems.

In most systems, the number after the letters represent the percentage of particles filtered. The exception are P, FFP and D ratings. For more information on these, I recommend reading this post on respirator ratings.

Mask Rating Systems

Comparison of FFP2, KN95, and N95 and Other Filtering Facepiece Respirator Classes (3M)

Read more: Xiaomi Purely mask review.

Are N95 Masks Reusable?

In regards to fine dust and non-viral particles, you can usually reuse a respirator until it becomes deformed, soiled, or difficult to breathe through. If the mask gets wet or moist (makeup, lipstick, humidity, etc), it should be disposed of.

In medical situations, N95 respirators are rated for 8 hours of use (CDC). However, in mask shortages it is possible to reuse N95 respirators if the correct sanitary precautions are followed. Sages has an article on cleaning methods that are currently looking promising.

For a reusable > 95% efficient mask, consider looking into Cambridge Mask or Vogmask.

What Is a P100 Mask?

Similar to N rated masks, the number represents the filtration. Therefore, in P100, the 100 stands for 99.97% filtration of 0.3 micrometer particles (CDC).

The letter represents the oil resistance. An N rated mask is not resistant to oil, R rated mask is oil resistant, and P is strongly oil resistant.

Therefore, a P100 mask is strongly oil resistant and filters 99.97% of fine particles.

Is P100 Better Than N95?

In terms of filtration, yes, P100 will provide better protection than an N95 respirator.

95 represents the filtration efficiency of the mask (95%), whereas 100 represents a 99.97% filtration. However, N99 and N100 respirators can also be found, and these provide very similar filtration to P100.

However, for general use P100 isn’t necessary and may even be more uncomfortable due to increased breathing resistance. P100 is designed for situations in which oil resistance is needed.

Purchase P100 Respirator: P100 Respirator | Alternative Link

What Is the Difference Between a Mask With a Valve vs No Valve?

There is a lot of confusion over the difference between respirators with a valve and those without. Generally, people seem to consider those with valves as superior (maybe because they look cooler?). However, this isn’t always the case.

Valves have two main purposes. One is to decrease humidity within the respirator (which increases comfort as well as the longevity of the respirator), and one is to decrease breathing resistance, making the respirator more comfortable to breathe through.

As 3M states on its Cool Flow Valve ‘The proprietary 3M™ Cool Flow™ Valve is designed to release your hot, humid exhaled breath quickly, helping to prevent an unpleasant build-up of heat inside the facepiece – a significant cause of discomfort to respirator wearers.’ (3M)

From that statement, it’s easy to think that valved masks are just superior. However, there are some cases in which masks without a valve are better. 

Valves mean that air that is inhaled is filtered, but exhaled air can pass out of the mask unfiltered. This means that for situations where you are trying to filter your own breath they aren’t ideal.

An example case is with the prevention of virus spreading. A valved mask is not the best choice as you generally want a mask that protects both you, and those around you. A mask with a valve only protects you.

‘N95 respirators with exhalation valves should not be used when sterile conditions are needed’ (U.S FDA).

How Can I Tell the Difference Between a Respirator and Mask?

Respirators are often confused with masks and this is perhaps the biggest confusion that I see. What is the difference between a respirator and a mask? ‘Mask’ is a rather broad term and can refer to many different things. However, generally the word is used to refer to surgical masks (those which you will see surgeons wearing in movies). These masks do have their purposes, 

As the Centre for Health Protection in Hong Kong states ‘Face mask provides a physical barrier to fluids and large-particle droplets. Surgical mask is a type of face mask commonly used. When used properly, surgical masks can prevent infections transmitted by respiratory droplets’ (Hong Kong CHP). 

In other words, surgical masks are intended to protect the wearer and those around them from droplets. They will not filter fine particles such as fine dust or airborne viruses. 

A respirator will always have some kind of rating. While the rating depends on your region, they will usually have an NIOSH (N95, N99, N100) rating. However, they could have another rating such as FFP, KF, KN, P, etc.

A respirator will filter fine-particles and they are normally measured on their ability to filter particles at 0.3 microns in size.

CDC Surgical Mask VS Respirator

The CDC made this fantastic infographic comparing surgical masks and respirators.

At What Aqi Should I Wear a Respirator?

There is no clear answer to this and it is up to the user’s discretion. Generally, 100-150 AQI is considered unhealthy for sensitive groups (such as those with asthma), and 150+ is considered unhealthy for all (Airnow). If you are wondering how to find the AQI, I recommend checking out these AQI apps.

If you are experiencing difficulty breathing or other respiratory symptoms, contact your doctor. If you are concerned, there is no loss in wearing a mask.

Are Masks Effective Against Smaller Particles (Such as Viruses)?

Since NIOSH and most other regional ratings are based on filtration of 0.3-micron particles, it begs the question ‘are respirators effective against smaller particles?’. The answer is yes. They often are.

Since masks aren’t rated at their capability to filter these smaller particles, there is no guarantee. However, a recent study by 3M did find that out of 6 N95 masks, they all offered between 90-100% filtration of smaller particles. 

Even virus particles as small as 0.02 microns are filtered at around a 95% efficiency with the tested N95 respirators. 

Virus particles range from 20 nanometers to 250 nanometers, or 0.02 microns to 0.25 microns. In other words, respirators are capable of filtering even the smallest virus particles. However, the exact filtration capabilities differ by model, and even within models.

Some masks, such as MeoAir have been tested to have greater than 99% filtration efficiency of particles at 0.1 micro-metres in size. For more information on this phenomenon, please refer to this article on filtration mechanisms and most penetration particle size.

If you are interested in a mask that is created specifically for viruses, I recently reviewed the Craft Cadence Nanofiber Mask.

Respirator Virus particles

A study by 3M shows six N95 respirators performance on particles from 0.01 um to 0.2 um.

N95 rated respirators3M 8511 N95 | 3M 8210 N95

Can You Wear a Respirator With Facial Hair?

In short, no. You can not expect a respirator to be effective if you have facial hair, and those with facial hair were found to have between 20 and 1000 times more leakage than those without (CDC).

However, if your facial hair is contained within the mask (and doesn’t prevent a seal from being made), then a respirator may still be effective. 

There is a fantastic infographic showing which facial hair styles are okay with a respirator.

Facial Hair Respirator

Facial Hairstyles and Filtering Facepiece Respirators (CDC)

How Can I Tell If a Respirator Is Real?

With the number of respirators out there, and with many people trying to make some quick money, it can be hard to tell which respirators are real.

Unfortunately, there is no easy way to tell this as there are many different respirator rating systems out there. However, generally, respirators will have a rating as well as the standard codes that they meet located on the respirator itself.

For NIOSH respirators, you can also check this link.

NIOSH Mask Rating Labels

Filtering Facepiece Respirator (FFR) Labels (CDC)

How Do I Wear a Respirator?

Wearing a respirator correctly is the most vital step, and usually where most people get it wrong. A respirator worn incorrectly is not effective.

After donning a respirator, the device must be checked for leaks. Both a positive and negative seal check should be performed to check for leaks.

Respirator Wearing Guide

How to Properly Put on and Take off a Disposable Respirator (CDC)

N99 reusable respiratorsMuryobao N99 Respirator | Cambridge Mask N99 (my recommendation) | Cambridge Mask (Ebay)

Can a Respirator Be Effective Without Fit-Testing?

For respirator to be fully effective, the wearer must undergo professional training. There is no alternative to being professionally trained and fit tested.

However, there is some evidence to show that respirators can lead to a reduction in exposure to fine particles for those without fit-testing and training. 

For this to be the case, the wearer must know how to don a respirator, perform a seal check, be clean-shaven, and make sure no clothing or jewellery gets between the respirator and face. There are also some respirators that allow the user to self fit-test.

For more information on to do these steps correctly, please refer to this guide.

Can You Clean an N95 Mask?

Generally speaking, no, you can not clean and reuse NIOSH rated respirators. Some reusable masks such as Vogmask and Cambridge Mask however, can be cleaned and reused.

Due to the current lack of respirators globally, methods for disinfection are being investigated. Information is currently being updated daily. As of writing this post, the methods supported by current data are Hydrogen Peroxide Vaporization, UV treatment, Moist Heat and Dry Heat (SAGES).

Any method of cleaning that soils, deforms, or reduces the electrostatic charge of the N95 respirator should be avoided. (SAGES)


I hope that this post can help give you the answers to some questions that you may have had. If you have a question that wasn’t included on this list, please contact me or comment below. I will do my best to find the answers and add them here.

If you notice any inaccuracies or have any further comments, please don’t hesitate to contact me. I will up

Read 2 Comments on 'Respirator Frequently Asked Questions'

  1. Does the KN95 mask also have an only one-way air-filtration valve (like an N95)?
    Are there mask types which have a bi-directional air filtration valves? However, an uninfected user of a KN95 or N95 would not, I suppose, be putting others at risk by wearing such masks with expiration valves ?

    1. Both N95 and KN95 will provide bi-directional filtration provided they don’t have a valve.

      There are some masks that feature valves with bi-directional filtration. However, I am not sure if any of these are officially rated N95/KN95. I will have a look online and see if I can find any.

      You are right – if a person is uninfected then a mask with and without a valve would both perform very similarly. The issue is that often the wearer does not know whether they are infected or not – since there can be a long period with little (or no) symptoms, wearing masks with bi-directional filtration is very important.

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