A KN95 mask is a half face, air purifying facepiece respirator. It protects the wearer from harmful non oil particulate (not gaseous) matter. Non medical KN95s are subject to the Chinese GB2626-2006 standards for this class of respirators.
The GB2626-2006 standards are broadly equivalent to the standards to which non medical N95 masks are set. The N95 standards are however set by the National Institute For Occupational Safety & Health (NIOSH) in the United States.
The NIOSH also sets performance standards for other types of facepiece respirators such as P95 masks. These filter both oil and non oil particles.
As stated, the KN95 and N95 respirators are governed by US and Chinese standards respectively. However, it must be noted that both classes of respirator are mainly manufactured in China.
The technology used in both N95 and KN95 masks was developed in the early 1990s. The scientist responsible was a Taiwanese American materials scientist named Peter Tsai .
Tsai developed the masks using electrostatic filtration technology. This involved the use of non woven material that contained both positive and negative charges. This material was able to attract small particles – mainly dust, bacteria and viruses – and trap them to prevent penetration of the mask. He patented the invention in 1995.
KN95 and N95 masks were initially used primarily for industrial purposes such as mining, construction and renovation. The masks were later adapted for use in medical facilities. The KN95 masks used in medical applications are however subject to slightly different performance standards than those in industrial or commercial applications. We expand more on this difference below.
Performance Standards For KN95 Masks
Non Medical Masks
In general, the GB2626-2006 non medical standards require the following performance levels from KN95 masks:
They must demonstrate a 95 percent filtration efficiency of non oil salt sized (0.3 microns or larger) particles. This should be at a particle flow rate of 85 L/min. This is the origin of the “95” in their name.;
The standards require them to protect the ability of the wearer to breathe adequately. Specifically, they are subject to maximum inhalation and exhalation resistance standards of 350 Pa and 250 Pa respectively;
KN95 masks should demonstrate less than stipulated maximum levels of leakage of contaminated air between the edges of the respirator and the wearer’s face. These are known as Total Inward leakage (TIL) standards.
The GB2626-2006 standards also require non medical KN95 masks to be tight fitting to the face and free from deformation. The TIL standards define what is meant by “tight fitting” for this purpose.
Although most KN95 masks use ear loops as their harnessing mechanism, this is not a requirement of the GB2626-2006 standards. Some KN95 masks (like the DynaPro KN95) use a head strap harness but are still compliant with GB2626-2006.
There are also performance standards as far as exhalation valve leakage levels are concerned. However, the KN95 respirator masks in this section do not have exhalation valves, so those standards do not apply here.
Each non medical KN95 mask should be labelled with the number and year of publication of the applicable standard.
For the GB2626-2006 standard, for example, the label should read “GB2626-2006”. The label should also show the type and grade of filter elements e.g. “KN95”.
Medical KN95 Masks
As mentioned above, KN95 masks were adapted for use by health care workers in medical facilities after being primarily used for commercial purposes. A slightly modified set of standards (currently GB 19083-2010) was developed for KN95 masks used for medical purposes (sometimes called surgical respirators).
The primary differences are:
Medical KN95 masks do not need to carry any labelling information;
The nasal splints used for medical KN95 masks must be adjustable, whereas those for non medical masks do not need to be;
The inhalation resistance standard for medical KN95s is slightly more stringent than that applicable to non medical masks (343.2 Pa vs 350 Pa). However, there is no exhalation resistance standard for medical KN95 masks;
Medical KN95 masks need to meet “synthetic blood penetration resistance” standards. Specifically, the masks should resist blood penetration when 2 mL of synthetic blood is spayed on them at 10.7 kPa. Non medical masks, by contrast, are not subject to any corresponding performance standard;
The GB 19083-2010 standards also impose “Bioburden” standards for medical KN95 masks. This consists of maximum levels of bacterial and fungal counts that may be present on the surface of the mask;
The Total Inward Leakage (TIL) standards to which non medical KN95 masks are subject do not apply to their medical counterparts.
One key difference (included above) between medical and non medical KN95s is the requirement that the former be able to resist synthetic blood penetration. This is similar to the distinction that exists between disposable non medical and surgical masks. The reason for this difference lies in the fact that the medical versions of these masks should be capable of use in surgical or other situations in which there may be spraying of blood or other bodily fluids.
Uses Of KN95 Masks
Commercial / Industrial Uses
KN95 face masks are in widespread use in environments that pose a threat to workers’ well being. This includes environments with dust, paint thinner or other particles that could cause harm if inadvertently inhaled. As a result, they are widely used in industries such as mining and building construction or renovation.
Protection From Viral Or Bacterial Particles
KN95 face masks that comply with the GB2626-2006 standards are eligible for use as personal protective equipment (PPE). In this capacity, they will resist penetration by potentially harmful viral and bacterial particles.
Many viral and bacterial particles can be as small as 0.1 microns. However, they are transported on larger respiratory droplets such as those we emit while coughing, speaking, sneezing or even breathing. As a result, KN95 face masks, by blocking the larger respiratory droplets, can also resist penetration by viral and bacterial particles.
The demand for KN95 respirators for protection from viral pathogens has risen significantly in the past year. This is a result of the spread of the Covid-19 virus.
However, in addition to the Covid-19 virus, KN95 masks are capable of resisting penetration by other harmful pathogens. These include viruses such as avian influenza, Ebola and severe acute respiratory syndrome (SARS).
Limitations Of KN95 Masks
As stated above, KN95 masks meeting the GB2626-2006 standard will filter 95 percent of non oil particles of size 0.3 microns or larger. However, these masks are not suitable for:
Use in environments containing oil particles such as cutting fluids, lubricants or glycerine;
Firefighting or other activities in which the atmosphere may be oxygen deficient;
Use in environments where hazardous gases or vapours may be present (since KN95s protect against particulate matter and not against vapours).
Guidelines issued by the US Centers for Disease Control and Prevention indicate that N95 respirators should ideally not be reused in environments with a high risk of contamination by viral or bacterial particles. This restriction is also applicable to KN95 masks as well as other N95 equivalent face coverings.
Even if they are not being used in environments with a high risk of contamination, users should not reuse KN95s indefinitely.
Instead, they should replace the masks within a specific period of time such as after 3-4 weeks of daily use. They should also be immediately replaced if they become wet or are soiled by any other foreign substances.
Finally, due to the risk of blood penetration, non medical KN95 masks should not be used in surgical or other environments in which the wearer may be exposed to spraying of blood or other bodily fluids.