Originally manufactured for industrial use, N95 masks filter more than 95% of the airborne particles from entering the wearer’s system. Originally, they were manufactured to help the industry workers against the chemicals they work around and harmful industrial wastes. Some other types of highly effective masks include N99 and N100 masks (effectively filter out 99.93% particles). Nowadays, N95 masks have gained popularity due to their increased use in the fight against the coronavirus pandemic.
N95 masks come in a variety of shapes and sizes, making it easier for the health workers to find something compatible with their face shapes. However, it is not very effective against the intruders while using on a beard, as the sides are not completely locked. It is important to notice that N95 masks are not genuinely designed for health workers. The one used by health workers is grade II N95 masks approved by the Food and Drugs Administration (FDA) and the National Institute for Occupational Safety and Health (NIOSH).
How does N95 mask work?
The N95 masks are made up of a fine mesh of synthetic polymer fiber, and interwoven polypropylene fabric. Thanks to its interwoven fabric, the intruder viruses or bacteria cannot go through it and get stuck. The particles after being stuck are forced to make twists and turns in a network of interwoven fabrics, causing it to get more stuck. This special fabric also attracts more particles, causing them to stack up and creating a more efficient filter. However, it makes the filter to be difficult to breathe through, hence they are made disposable.
How are N95 masks made?
A clinical N95 respirator comprises of various layers of nonwoven texture, regularly produced using polypropylene. The two outward guarded layers of surface, covering inside and outside of the shroud, are made using spun holding. Spun holding uses spouts blowing mollified strings of a thermoplastic polymer (normally polypropylene) to layer strings between 15-35 micrometers on a vehicle line, which joins up with texture as the belt continues down the line. Strands are then sustained using warm, mechanical, or synthetic techniques.
The two outside layers of the respirator, some place in the scope of 20 and 50 gram for every meter square in thickness, go about as confirmation against the outer condition similarly as a limit to anything in the wearer's exhalations. Between the spun bond layers there's a filtration and a pre-filtration layer, which can be as thick as 250 grams for each meter square. The pre-filtration layer is typically a needled nonwoven. The nonwoven material is a needle punched to expand its cohesiveness, practiced by sending needles more than once through the texture to snare filaments together.
The pre-filtration layer is then gone through a hot calendaring measure, in which plastic strands are thermally fortified by running them through high weight warmed rolls. This makes the pre-filtration layer shaped to outline the ideal shape and stay in that shape as the cover is used by making it thicker and stiffer. The last layer is a high-proficiency liquefy blown electret nonwoven material, which decides the filtration productivity.
Melt-blowing is a cycle like spun holding, in which numerous machine spouts use air to splash strings of dissolved engineered polymers onto a transport. Nonetheless, these strands are a lot littler, as not exactly a micron wide. The full respirators are made through changing over hardware, which joins the layers through ultrasonic welding and adds ties and metal strips to modify the cover over the client's nose. The respirators are then disinfected as the last advance before being delivered.
Testing of N95 masks.
Like the surgical masks, N95 masks go through a series of tests to determine their effectiveness, under the CDC. They are conditioned for 24 hours before testing, under 38 C temperature and 85% relative humidity. They are tested with the following.
- First the test for particle penetration is conducted with charge neutralizes sodium chloride aerosol spray. This features particles with a median of 0.3 microns in diameter, for effective testing.
- An airflow of 85 L per minute is introduced to test the effectiveness of the N95 mask in a workflow environment.
At least 200 mg of aerosol spray is introduced, which clogs up the filter and simulates a high level of exposure.
These N95 respirators are also tested for a wide scope of purposes such as inflammability, biocompatibility, and so on. In normal circumstances, the FDA and NIOSH both test and approve the masks. However, due to COVID-19 pandemic, NIOSH-approved respirators, not regulated by the FDA, are being distributed for the use of health workers.
The basic purpose of N95 masks is to capture 95% of the particles from the air and provide protection against them. Hence theoretically, it is not compulsory to make them from the above-mentioned materials. They can be manufactured by any eco-friendly material as long as it filters out 95% of the airborne particles such as bacteria, dust particles, and viruses. As long as the basic purpose is being fulfilled, the composition does not matter.
Due to the high demand and popularity, N95 masks are also being manufactured at a low scale, by local producers. However, the most famous producers are 3M and NIOSH, in the US, also supplying worldwide. In the race against this pandemic, N95 masks are becoming a necessity for both the health workers and the general public alike.