Two types of respiratory devices exist: filtering and providing. A N95 respiratory device or mask prevents bacteria and contaminants from reaching your nose, mouth, and throat. Clean air supplying respirators provide clean air from a tank, or any other uncontaminated source (for instance an SCBA). N95 respirators have become a very popular product as healthcare workers across the U.S. face shortages when treating COVID-19 patients.
We'll be discussing the basics of N95 respirators manufacturing, such as their purpose, how they are made and the testing methods used to determine their quality. Our How surgical masks made guide will help you if you are more interested in how they are made . A guide is also available on the best cloth masks and the best surgical masks for at-home use.
What are N95 Masks and How Do They Work?
N95 respirators, originally developed for industrial purposes, are specialized masks which filter out at least 95% all particles greater than.3 microns. N99 and N100 respirators can also be used. N100s block at least 99.97%. The FDA and NIOSH (National Institute for Occupational Safety and Health), have both approved genuine surgical respirators. There are many N95s available, and they can be customized to fit different faces. They cannot seal beards, however. Some N95s come with exhalation valves which allow for easier breathing.
It is important to remember that not all N95 respirators have been designed for medical use. Others are intended for industrial purposes. N95s for medical use are class II products regulated by FDA (Food and Drug Administration), and NIOSH.
Also, recent reports by Health line as well as the CDC indicate that masks that have vents or valves are less likely to spread disease. While the masks offer the same protection as an invented one, the valve does nothing to prevent viruses from entering the body. This could allow people to spread the virus, even if they are not aware that they have been infected. The virus can also be spread by a face mask without a mask.
How do N95 Masks Work?
Because of the structure and non woven material, N95 respirators filter out particles. Particles can get caught in the dense network of fibers that make up the non woven material. They are as thin at one micron. The masks are also electrostatic ally charged to attract more particles. The mask acts as an efficient filter by trapping particles. However, masks can become more difficult to breathe through due to the buildup. This is why disposable filters and masks have been developed.
CDC Updated Guidelines about N95 Usage
Update July 2021 Healthcare organizations will be returning to the use of standard masks. In addition, the FDA has revoked EUAs issued to non-NIOSH-approved respirators including KN95 mask. It advises healthcare workers to use disposable respirators only for one time and not over extended periods. This is in accordance with OSHA and the CDC's new standards.
The latest guidelines have been published by the CDC to assist healthcare professionals in obtaining N95 mask for limited supply during this outbreak. Some measures include:
- For applications outside of the operating area, do not use masks beyond their expiration date. It's crucial to verify the seal if masks are being used while patients are actively treated.
- You can use respirators that have been approved under the same foreign standards as China's GB2626-2006, GB2626-2019 standards and European EN 149-2001 standards.
- N95s may be limitedly reused by multiple patients. However, it should be removed between each encounter. If there is no manufacturer guidance, the CDC recommends a maximum five reuses. Workers can cover N95s with cloth masks to preserve them.
- Prioritize N95 Masks for the most risky activities, such as aerosol-generating medical procedure (such as close contact with patients unmasked) and surgery.
The CDC recommends that healthcare workers be protected by administrative controls. This includes a decrease in hospital stays for patients with coronavirus and suspension of fit testing masks. In situations where there are no N95s, the CDC recommends keeping healthcare workers at high risk of severe illness from patients with coronavirus and having those who have the virus care for them. It is not known if those who recover are immune to the virus.
The CDC offers some suggestions for extreme cases. Learn more in our article cleaning N95 Masks.
How are N95 Masks manufactured?
The medical N95 respirator is made up of many layers of non woven fabric. It's often made out of polypropylene. Spinned bonding is used to create the outer protective layers that cover the mask's interior and exterior. Spun bonding involves using nozzles to blow melted threads of thermoplastic polymer (often, polypropylene), which layer threads between 15-20 and 35 micrometers on a conveyor line. As the belt moves down the conveyor belt, the threads become cloth. The fibers can then be bonded using mechanical, chemical, or thermal methods. The respirator's outer layers, which are 20 to 50 g/m 2 in thickness, serve as protection against the external environment as well as a barrier for any inhalations.
The spun bond layers are separated by a prefiltration layer. This layer can be as dense 250 g/m 2. The prefiltration layer is usually needled non woven. The needle punching of non woven material increases its cohesiveness. This is achieved by running barbed needles through the fabric repeatedly to attach fibers. Next, the prefiltration layer goes through a hot calendaring procedure in which plastic fibers can be thermally bonded to each other by running them through heated rolls at high pressure. This makes the prefiltration layer thicker. It can then be molded into the desired shape, and it will stay that way as long as the mask is used.
The final layer of the filter is a high performance melt-blown electret or polarized non woven material. This determines its filtration efficiency. Melt blowing, which is similar to spun bonding uses multiple machine nozzles to spray threads made of melted synthetic polymers onto conveyors. These fibers are less than one micron in width. The threads are bonded by cooling as they cool and build up, creating fabric. The fabric may also be thermally bonded to improve strength and resistance to abrasion. However, some fabric characteristics are lost. The guide to how melt-blown fabric is made explains this process in greater detail.
Converting machinery creates full respirators. This involves combining layers of material through ultrasonic welding. The mask is then adjusted over the nose using metal strips and straps. As a final step, the respirators must be sterilized before they can be shipped.
Testing Methods for N95-Masks
N95s are subject to several tests just like surgical masks. While you can read more about the CDC's website in detail, this section will only give a brief overview. N95s at the CDC are subject to 24-hour conditioning in a 38-degree C environment and 85% relative humidity before being tested. During testing, the respirator must maintain its certification class level of filtration. Tests with N95 include:
- The aerosol spray contains particles that are.3 microns or less in diameter. This is a test for particle penetration.
- This test indicates a moderately high rate of work, with an airflow of 85 liters per minute.
- A test for breathing resistance at 35 mm, or below water column pressure. An exhalation resistance test at 25 mm, or below water table height pressure. (A millimeter water column pressure is the pressure equal to one millimeter of pressure at 39 degrees F.
- Minimum 200 mg aerosol loading. This simulates high exposure by clogging up your mask with aerosol particles.
FDA tests the respirators for flammability, bio compatibility and fluid resistance. Normal circumstances would require respirators to be approved by both NIOSH and the FDA. NIOSH-approved respirators, which aren't regulated by FDA, can now be used by healthcare workers. On the CDC's website, you can find more information about NIOSH approval as well as respirator testing and procedures. The FDA has removed all EUAs issued for disposable respirators not approved by NIOSH. Potential manufacturers are advised to consult the CDC's How to Apply for NIOSH Approval.
Conclusion
This guide will explain how N95 respirators are made and used. If you are more interested in N95 respirators, check out our article on top respirator and mask suppliers. Or, go to our supplier discovery page which contains detailed information about over 60 of the N95 suppliers. Register for our COVID-19 Response Suppliers if you believe your company can help fight coronavirus.
Also, you can see our overview guide Making PPE for CoVID-19 or Making Cloth Masks to help with COVID-19.
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