Understanding mask ratings can seem overwhelming at first, especially if you come from an industry or field where the knowledge isn’t commonplace. Understanding the difference between an N95 and R95 respirator alone is difficult, and that’s not to mention the many different mask rating systems used globally.
I myself knew little about respirators before moving to Korea. Here, they are essential on days of bad air pollution in Seoul, and it’s important to have at least a basic understanding so that you are able to protect yourself.
After spending days researching for articles on this website, I have come to learn a lot about respirators and masks. In that time, I have also come to realise how little most people know about them and the differences between the rating systems.
Further, with the recent panic around the world, masks are in more demand than ever. However, a lot of people are having difficulty comparing masks and making the right purchasing decisions.
In this post, I will compare the different rating systems, and point out what you need to know. By the end of this post, you will be able to make an informed purchasing decision and know that you are getting the best mask for your needs.
This article was created to help you answer the question of ‘what are the differences between N95, FFP2, KN95, KF94 and other mask ratings?’. Further, what are the similarities between the systems?
If you’re looking for a quick overview, please refer to the infographic below. This contains the most pertinent information regarding each standard. If you are interested in sharing the graphic, please feel free to do so with attribution. To learn more, read on!
Masks are only effective when fitted and worn correctly. Please refer to this CDC guide to donning a respirator for more information.
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 information and information is subject to change without notice.
Mask Rating Systems
‘Respirators with similar performance requirements to NIOSH-approved devices’ (CDC). However, there is still limited testing on these standards by CDC, and N95 is recommended where possible.
The biggest factor that makes understanding mask ratings so difficult to grasp is the number of different systems. The most commonly known mask rating is the NIOSH system, which rates masks as N95, N99, and N100. These masks are rated by the American National Institute for Occupational Safety and Health, which is part of the CDC.
But did you know that this is only the tip of the iceberg? Not only does the NIOSH also certify R and P rated masks, but there are also 6 other commonly used mask rating systems. Although knowing the NIOSH rating system is sometimes enough, in times when stocks are low knowing the other mask ratings can come in handy. After all, N95 masks are usually the first to sell out.
The most important rating systems to know are the NIOSH ratings (N95), and Europe EN (FFP2). These are the most commonly found masks and most other rating systems are based on, or closely follow, the guidelines of these respirators.
The other rating systems are the Korean KF ratings given by the MFDS (Ministry of Food and Drug Safety), Chinese KN and KP ratings given by the Standardization Administration of China, New Zealand & Australian P ratings given by the Joint Australian/New Zealand Standards Committee, Japanese DS ratings given by the Japanese Ministry of Health, Labour, and Welfare and Brazilian PFF ratings given by the Ministry of Economy (source).
While this may seem like an overwhelming number of standards, you can generally get away with only understanding the NIOSH and European EN mask ratings. This is due to the fact that all other systems are either strictly or loosely based on these systems. With this in mind, we can divide all mask ratings roughly into two categories:
Standards based on European EN specifications: FFP, PFF, KF, and P (Aus/NZ rated devices)
Standards based on NIOSH specifications: N, KN, DS
This isn’t to say that these standards are exactly the same in regards to specifications. There are minor differences between some. However, these standards have a lot of requirements and testing methodologies in common. For example, an FFP1, PFF1 and KF80 mask are identical in terms of performance, simply being rated differently due to local authorities and differing certifications.
Respirators are only rated for one use (typically of 8 hours). However, in times of need, they can be disinfected and reused. Learn more about respirator cleaning here.
U.S NIOSH Ratings
NIOSH masks should always have the above markings. CDC.
NIOSH rated masks are the most common masks that you will usually find. These masks come in three different letter variations, N, R, and P. These letters will be followed by a number, making a rating such as N99, R95, or P100. But what do these letters and numbers mean?
Luckily, the number is easy to understand. The number on NIOSH rated masks signifies the filtration efficacy of the filter. For example, an N95 mask is required to stop AT LEAST 95% of particles of 0.3 microns in size (source). An R95 mask will also filter out at least 95% of 0.3-micron particles.
The same logic applies to N99 devices, where the device will filter at least 99% of particles at 0.3 microns. The only difference comes in with N100 and P100 rated masks. Complete filtration is at this point impossible, and an N100 rated mask is effective at stopping 99.97% of 0.3-micron particles (source).
In other words, the higher the number the better the filtration efficiency. In most situations, the letter (N, R or P) is irrelevant. For particle filtration such as air pollution, these devices will perform the same – N100 and P100 masks are rated to filter the same percentage of particles. The same goes for N95 and R95 masks. However, R and P devices do have some differences.
NIOSH also sets guidelines for other factors such as inhalation and exhalation resistance at a flow rate of 85 L/min. Interestingly, NIOSH-certified devices are intended for professionals who have undergone fit-testing. As such, the standard doesn’t test for total inward leakage on human subjects – something that is required for a device to be certified KN95, FFP2, P2, KF94 or DS2.
Therefore, while NIOSH-rated devices, particularly N95s are seen as the golden standard, they are not necessarily the best choice for the standard person. N95 devices are not designed for general consumers and this is reflected in the lack of leakage testing on human subjects.
Best N95 rated respirators – 3M 8511 N95 | 3M 8210 N95 (only buy from trusted sellers)
N vs R vs P respirators
The letters on NIOSH rated respirators represent the oil resistance of the mask. N rated masks are not resistant to oil, R rated masks are somewhat resistant to oil, and P rated masks are strongly resistant to oil (source).
This means that for people wearing masks due to air pollution or viruses, only an N rated mask is needed. R rated masks can come in useful in specific situations, for example, if you regularly bike on busy highways near vehicles. An R rated mask will be more resistant to the fumes put out by those vehicles.
For the vast majority of people, N rated masks are all that is needed. R and P rated masks are generally used in workplaces that involve aerosols and that need to provide workers with the best protection (source).
Read more reviews: Airinum, Cambridge Mask, Vogmask & Totobobo.
European EN Ratings
EN149:2001 FFP3 Respirator from 3M.
The next most common masks that you will find are those rated according to the standards set by the European Union. These masks come in three different ratings, FFP1, FFP2 and FFP3. Although the numbers on these masks don’t have the same simplicity as the NIOSH-certified devices, the higher numbers are still better.
An FFP1 mask has 80% filtration, FFP2 has 94% and acts very similarly to an N95 mask, and FFP3 has 99% and performs similarly to an N99 mask (source). In short, other than the FFP1 rating, which performs significantly worse than any NIOSH rated mask, European EN rated masks perform similarly to their NIOSH equivalents – at least when it comes to filtration.
What sets European EN standards apart from their American counterparts is that these devices must undergo TIL (total inward leakage) testing on human subjects performing exercises. This means that each device must display ≤ 8% leakage on a range of different subjects. On top of this, FFP2 devices must display significantly lower inhalation resistance than N95 products.
Where NIOSH requires N95 devices to display a pressure drop ≤ 343pa, FFP2 standards mandate that a device must have a pressure drop ≤ 240pa at a higher flow rate (85 L/min vs 95 L/min). While this is the maximum value accepted, and many devices will be less, FFP2 devices will generally be more comfortable to breathe through due to their lower inhalation resistance.
The combination of TIL testing along with the lower requirement for pressure drop shows that the European EN standard is more aimed towards general consumers. While fit testing is still essential for the best protection, the lower breathing resistance requirement along with leakage testing may be a better choice for non-professional use.
When picking a mask for fine dust or other very fine particles, an FFP2 or FFP3 mask is highly recommended as they will perform substantially better against fine particles in the air. FFP1 devices provide only ≥ 80% filtration efficacy and are not ideal. However, they will generally have lower breathing resistance.
Purchase FFP2 respirators – FFP2 Respirator | FFP3 Respirator Mask (only buy from trusted sellers)
Chinese KN and KP Ratings
Chinese masks come rated as either KN or KP. Similarly to the NIOSH ratings, the letters represent oil resistance while the number represents filtration efficiency. KN and KP masks come rated as 90, 95, and 100 (source).
KN masks are the standard masks that are intended for the vast majority of wearers. These masks are not resistant to oil. KP masks, on the other hand, do provide oil resistance. KN and KP masks are both available in 90%, 95% and 100% (100% is actually 99.97%) varieties (source).
While the filtration, breathing resistance, and flow rate test requirements for KN95 devices are very similar to N95 masks, KN95 devices also require TIL (total inward leakage) testing. Similar to the FFP2 standard, KN95 devices must display ≤ 8% leakage on a range of human subjects performing exercises.
However, depending on your ethnicity, FFP2 devices may perform better. While both standards must undergo TIL testing, it’s worth noting that the test subjects likely have facial features common in a region. Therefore, while in theory KN95 and FFP2 devices have the same leakage requirements, users with different facial features may have different results.
It is worth noting that many KN95 devices do not perform to their specifications. Unfortunately, there are have been many issues with counterfeit devices over the past couple of years. While an authentic KN95 mask is a performant device, many aren’t authentic. This issue is enhanced as it’s hard to check the devices in a database as you can with N95, KF94, and many other masks.
Purchase KN95 respirators – KN95 Mask (only buy from trusted sellers)
Learn More: MeoAir Reusable Respirator with 99% filtration efficiency.
Korean KF Ratings
A standard KF94 rated mask.
There is some confusion surrounding Korean mask ratings as there are two different types – KF ratings and their occupational-use counterparts. KF- rated devices are designated for consumer use, whereas 1st Class (94% filtration) and Special Class (99% filtration) are meant for occupational use. 1st Class devices are considered as an N95 and FFP2 equivalent (source).
With that being said, KF94 devices are very similar to 1st Class devices. Both require ≥ 94% filtration and have the same TIL. The biggest difference is that 1st Class devices must meet stricter breathing resistance requirements. The standards the devices adhere to are also different, with KF94 devices following the MFDS notice No 2015-69¹ standard and 1st Class devices adhering to KMOEL-2017-64 (source).
While 1st Class devices are considered the exact equivalent of FFP2 and N95 devices, KF-rated devices are far more common as they are intended for public use. Korea’s Ministry for Food and Drug Safety also stated that KF94 and KF99 devices are equivalent to 1st Class and FFP2 and Special Class and FFP3 respectively (source).
Korean KF (Korea Filter) rated masks come in three different levels, KF80, KF94, and KF99. Like the NIOSH system, the number represents the filtration rate of particles, and this makes the masks very easy to compare. For example, a KF80 mask will filter 80% of particles at the MPPS.
The KF system is based on the European FFP rating system and as such, it performs almost identically. A KF80 mask performs the same as an FFP1 mask, KF94 will perform the same as an FFP2 mask, and KF99 will perform about the same as FFP3 (source).
Also identical are the pressure drop and flow rate requirements set by both the MFDS and KMOEL standards. Therefore, each tier of KF/Class mask has to adhere to identical standards as their European counterparts. The only difference is the breathing resistance in which 1st Class devices have stricter requirements.
If possible, use KF94/KF99 masks where possible, as they have significantly more protection than KF80 masks. In Korea, KF80 masks are often aimed at children and KF94 at adults. KF99 masks are far harder to find and are much less common than KF94.
Purchase KF rated respirators – KF94 Mask (only buy from trusted sellers)
Australian & NZ P Ratings
An Australian/New Zealand rated P2 Mask. Queensland Government.
P ratings are given by the Australian and New Zealand governments and are a bit harder to understand than most other systems. These masks can come rated at three different levels, P1, P2 and P3. As usual, the higher the number, the more effective the mask is. From the 3M website, these are the uses for each mask.
- P1 – used for mechanically generated particles eg silica, dusts, powders.
- P2 – used for mechanically and thermally generated dusts eg welding fume, metal fume.
- P3 – used for all particulates requiring high protection factors (source).
Similarly to the European EN standards, P1 devices will filter 80% of particles. The next tier, P2, will filter 94% of particles. P3 is capable of filtering ≥99.95% of particles but can only be achieved by full facepiece respirators (the devices that often use dual-cartridge filters and look like gas masks) (source). Therefore, only P1 and P2 particulate respirators are comparable devices to FFP1 and FFP2.
For fine particles, a P2 mask will perform similarly to an N95 mask. The New South Wales Government even calls a P2 respirator an N95 mask. P2 devices are also equivalent to FFP2, KF94, KN95, DS2 and PFF2 masks.
Interestingly, the P2 standard is stricter than almost all other standards when it comes to exhalation resistance. In theory, this should mean that P2 devices are much more comfortable to wear as they must adhere to stricter pressure drop requirements when it comes to exhaling.
Since P1 devices only filter ≥80% of fine particles, a P2 mask is generally recommended. If you’re looking for > 94% filtration, you will have to look elsewhere. FFP3, KF99 and N99 devices are good choices. If you are okay with a full facepiece respirator, P3 devices are also worth considering.
Japanese DS Ratings
The next commonly-used mask rating on this list is that issued by the Japanese Government. Similar to many of the other ratings on this list, the Japanese rating system follows the FFP system used by the European Union.
Japan rates masks as DS, DL, RS and RL followed by a number. 1 represents 80% efficiency, 2 is 95% and 3 is 99.9%. That is to say, a DS1 and RL1 mask have 80% efficiency against fine particles, RL2 masks have 95% efficiency, and an RS3 mask would have 99.9% (source).
Masks with D in the name are disposable masks whereas R masks have replaceable filters. Therefore, a DS2 and DL3 mask would be disposable, whereas an RS2 or RL3 mask are replaceable. When it comes to the second letter, S or L, this signifies the test particle that the device was exposed to (source).
Dioctyl phthalate (DOP) is used in L series devices (DL and RL) and is the same test particle that NIOSH R and P devices are exposed to. DOP is a liquid particle and an oil aerosol (source). As such, DL2/RL2 devices are equivalent to R95 devices. DL3/RL3 devices compare to P100.
Devices containing an S in their name have been tested against sodium chloride particles – the standard for mask testing. As such, DS2 and RS2 devices are the equivalents to FFP2, N95 and KN95 masks. A small note here to keep in mind is that, unlike FFP2, P2 and FPP2 ratings, the second tier of the Japanese system, DS2, actually filters ≥95% of particles rather than 94%.
Interestingly, DS-rated masks do not have an inward leakage requirement. However, where NIOSH-rated devices don’t require inward leakage testing at all, DS masks do undergo this testing. Instead of there being a requirement, the inward leakage results will be included in the device’s instructions. Therefore, it’s worth double-checking the instructions for these devices.
Brazilian PFF Ratings
I must admit that the first time I saw the term PFF2, I thought that someone had made a mistake when typing FFP2. However, these are different standards – albeit with extremely similar criteria. While I’m sure these devices are far more common in Brazil, they are rarely seen internationally.
PFF rated masks are certified according to the ABNT NBR 13698:2011 standard. This standard defines the tested particle size (mass average diameter of 0.3μm), maximum resistances, test particle type, and more. In testing methodology, this standard is almost identical to the European EN standard (source).
The PFF ratings follow the European FFP ratings (and therefore KF and P ratings) very closely. Divided into three tiers, PFF1, PFF2 and PFF3, these respirators provide 80%, 94% and 99% filtration respectively. Therefore, a PFF1 mask will provide the same filtration as an FFP1 or KF80 mask. PFF2 performs on the same level as FFP2 and KF94 devices, while PFF3 masks perform similarly to FFP3 and KF99 products.
However, unlike these other devices, the FPP certifications do not have a TIL requirement. Where every standard on this list – with the exception of NIOSH-certified devices – requires TIL testing, this standard does not.
Which Mask Rating is Best?
Now that we have covered the different mask ratings, it’s time to compare them and to see which is the best. Obviously, the best mask depends on the situation, however, for this section I am using the assumption that you don’t need an oil-resistant mask. Further, I am assuming that the mask is being used for standard particles, such as fine dust (as opposed to viral particles or otherwise).
There is no single ‘best’ rating. N masks are not inherently better than FFP masks, for example. As the table from 3M below shows, every different rating system has a comparable mask around the 95% filtration bracket.
3M’s Comparison of FFP2, KN95, and N95 and Other Filtering Facepiece Respirator Classes
As the table above shows, every system has a mask that provides around 95% filtration. Further, all standards have a mask that provides >99% filtration. With that being said, only some standards (FFP1, KF80, P1, DS1 and PFF1) offer a low-performance mask that provides ≥ 80% filtration.
It’s important to realise that any mask rating is better than none. A mask with any rating on this list will perform better than a standard surgical mask. Further, each rating system has a range of levels, often with 3 different tiers.
If you want the absolute best respirator, look into those with a rating of around ≥ 99%. This means N99, FFP3, KN100, or any comparable mask. Even a P100 mask is an option if you don’t mind spending a bit more. However, these devices often sacrifice breathability and may not be the best choice for general use.
Respirators with a rating similar to N95 also work very well. Masks such as KF94, FFP2, P2, and KN95 are all great options and provide good protection against fine dust and other small particles. These devices are often better for daily use as they tend to provide better breathability.
Mask Rating Comparisons
When comparing the specific ratings, there are three main brackets. Masks that offer ≥ 80% filtration (also including KN90 and KP90 devices), ≥ 94% filtration, and ≥ 99% filtration (including devices with 99.97% filtration).
≥ 80% Filtration: FFP1, KF80, KN90, P1, DS1, RS1, PFF1 (Oil resistant: RL1, DL1, KP90)
≥ 94% Filtration: FFP2, KF94, KN95, P2, N95, DS2, RS2, PFF2 (Oil resistant: R95, P95, RL2, DL2, KP95)
≥ 99% Filtration: FFP3, KF99, KN100, P3 (full face) N99, N100, DS3, RS3, PFF3 (Oil resistant: P100, RL3, DL3, KP100)
The graph below is a fantastic example of the different respirator brackets and how they compare. The dots on the lines represent individual respirators that were tested within each rating system. While the line only compares NIOSH and KFDA devices (Korea Food and Drug Association, now the MFDS), it’s important to remember that the KF system is based on the EU FFP system.
‘In Korea, since the EU standard was adopted, the efficiency requirements specified by the Korea Ministry of Labor (KMOL) for Second, First, and Special series are the same as the European requirements for FFP1/P1, FFP2/P2, and FFP3/P3, respectively’ (source).
Since all commonly-used certifications are based on either the NIOSH or European EN standards, we can assume that most equivalent devices will perform similarly to these standards. Of course, this only applies to authentic devices that adhere to these requirements.
Aerosol and Air Quality Research, Comparison of Filtration Efficiency and Pressure Drop in Anti-Yellow Sand Masks, Quarantine Masks, Medical Masks, General Masks, and Handkerchiefs.
Level 1: FFP1, KF80, PFF1, DS1, P1
In the first bracket, we find KF80, FPP1, DS1, RS1, P1, and PFF1 rated respirators. However, there isn’t much difference between these devices. Since most of these rating systems are based on that of the EU, these masks are mostly identical in terms of specifications. Due to this, it’s better to pick whichever mask fits your budget and face better.
Perhaps the biggest difference is that FFP1, KF80 and P1 devices must undergo TIL testing. Masks certified in Japan must include the leakage results in their instructions, but there is no requirement built into the standard. PFF1 devices area also excluded from requiring TIL testing.
While these devices do provide protection, it’s important to remember that these masks are only rated at 80% filtration. All of these masks are far less effective than those in the next bracket (94-95%). Admittedly, these masks will often provide better breathability and therefore may be better in situations where lower filtration is needed.
If you’re looking for an oil-resistant mask in the category, DL and RL products are the only option at ≥ 80% filtration. KP90 devices from China are also oil-resistant but sit at ≥ 90% filtration.
Level 2: N95, KN95, FFP2, KF94, DS2, P2, PFF2
The second mask bracket has a lot more options. It is worth noting again, that since KF94, PFF2 and P2 respirators use the same specifications as FFP2 respirators, this comparison is really between N95, KN95, DS2 and FFP2 respirators.
Both N95 and KN95 rated masks are effective at filtering out at least 95% of fine particulate matter. On the other hand, FFP2 masks are rated at 94%. For this reason, N95 and KN95 masks are very slightly more effective than FFP2 and KF94.
However, the difference is minimal and as the graph above shows, some FFP2 and KF94 masks can filter a significantly higher percentage of particles than 94%. If you are looking for certainty, however, an N95 or KN95 mask is the best.
KN95 masks from China should perform very similarly to N95 masks, and the table above shows that the differences are very minor. However, it’s very hard to find further information on KN95 masks in English. Further, it’s far easier to verify the authenticity of an N95 mask. For that reason, N95 masks are typically the best in this bracket.
FFP2 and their equivalent devices are a close second in terms of filtration. However, in terms of comfort, these devices are often better than their NIOSH-certified counterparts. They generally have more breathability and some devices – such as KF94 devices – are designed for public use. As such, they are designed without fit-testing in mind.
Level 3: N99, KF99, FFP3, DS3, PFF3, KN100, N100
In the last, and highest-rated bracket, are the 99 and 99.97% filtration respirators. These are the best respirators that can be purchased and offer the best protection against fine and ultrafine particles. As with the level 2 masks, this category can be simplified as many devices closely follow the European EN standard and therefore don’t need to be compared.
N99, FPP3, KF99, DS3, and PFF3 are all comparable and offer 99% filtration or higher. However, as with the above categories, KF99 devices are designed for public use and are likely more comfortable and better designed to be used without fit testing.
With that being said, N100 and KN100 respirators are both rated to filter 99.97% of particles at 0.3 microns, and this makes them more effective than FFP3 and N99 respirators. These are the devices that you will want to use if you are looking for the highest particle filtration available.
The notable exclusion here is P3-rated devices. As mentioned, this rating is available only for full-face respirators. As such, these devices don’t sit at this level, but rather compare with P100 and KP100 devices.
Level 4: P100, P3, KP100
Half-face reusable respirator. Queensland Government.
The final respirators on this list are not for general purposes. These respirators are rated by the NIOSH (P95, P99, P100) and the KP (KP90, KP95, KP100) respirators are rated by the Standardization Administration of China. The difference with these respirators compared to others on this list is that they are oil resistant.
KP100 respirators are oil-resistant and P100 are strongly oil-resistant (source). All of these masks are rated for 99.97% filtration, similar to the non-oil resistant variants.
P3 devices also have similar functionality and are designed to filter highly toxic and irritant particulates. Some filters are also designed for gas filtration (source). All of these respirators are designed for occupational use by professionals.
With all of the confusion surrounding respirators, I hope that this post has clarified the rating systems and helped you to pick the right mask for your situation. I will be updating this article in the future and adding information where possible.
While respirators can protect the wearer from fine particles, it’s important to remember that they will only do so if they are fitted correctly and handled well. If you are unsure how to fit a mask correctly, please refer to this article by the CDC.
If you have any questions or have noticed any inaccuracies in this post, please don’t hesitate to reach out to me. You can do so either below, by commenting, or by emailing me at [email protected].
Mask Rating FAQ
Are N95 and KN95 the Same?
No, these are two different rating systems. N ratings are given by the U.S NIOSH. However, KN ratings are given by the Standardisation Administration of China. However, both ratings do feature many similar characteristics.
Is FFP2 the Same as N95?
FFP2 rated respirators feature similar characteristics to the N95 rating, especially in regards to filtration. However, the ratings are used in different regions and do have some differences.
Why Are There So Many Different Ratings?
Many regions of the world have developed their own rating systems that meet the local market requirements. Further, some systems are aimed at specific sectors, whereas some are aimed at public use.
What Is the Difference Between N95, R95 and P100?
All of these masks are rated by the NIOSH. However, the difference comes down to oil resistance. N95 masks are non-oil resistant, R95 masks are lightly oil-resistant, and P100 are oil resistant.
Your post mentions “Korea has its highest rating at KF94”. This is not true. KF99 respirators exist and have a Particle Filtration Efficiency of ≤ 99 % (Test for Sodium Chloride & Paraffin Oil), a Breathing Resistance of ≥100 Pa and a Total Inward Leakage of ≥ 5.0% as mentioned in this MFDS document:
They are however very rare, e.g.
Thank you for your comment. You are right! That’s a mistake I will correct, I appreciate you pointing that out.
Ethan, thank you for compiling such helpful information. This is so appreciated!
One thing that I’m still baffled by is how should we compare these respirators with masks that claim they have been tested at a high filtration rate?
For Example, this Forbes article states that the HalO and aR masks have been tested and show about a 99% rate. Does that then mean that they are comparable to the 99-100% (KF99, N99, P100, FFP3, KN100) Bracket you discussed?
If not, how are they different? What’s important to consider in comparing them?
Korea’s highest rating is not KF99 as previous person said, that is the highest rating for PUBLIC use. The higher rating is for medical use and is shown in the 3M chart, the Korean 1st Class KMOEL-2017-64 standard.
Thanks for all of this info! Do you know if the KF ratings or approval by MSDS also consider safety of the mask, as in what chemicals may be in it or how safe they are to breathe through? Trying to make sure the masks are safe for my child to use all day long. Thanks!
This was extremely useful to me. Thanks.