How Surgical Masks Are Made & Tested?
Layered surgical face masks are made by combining non-woven fabric, which has better bacteria filtration and air permeability while remaining less slippery than a woven cloth. The material most commonly used to make layered surgical masks is polypropylene, either 20 or 25 gsm or grams per square meter in density. Face masks can also be made by using polystyrene, polyethylene, polycarbonate, or polyester.
Layered surgical masks are made up by covering a layer of textile with non-woven bonded fabric on both sides. Non-woven face masks, which are cheaper to make, thanks to their disposable nature, are made with three or four layers. These disposable face masks are often made with two filter layers effective at filtering out small particles such as bacteria above 1 micron. The filtration level of a layered surgical face mask, however, depends on the fiber, the way it’s manufactured, and the fiber’s cross-sectional shape. These surgical face masks are made on a machine that assembles the non-wovens with the help of bobbins, ultrasonically welds the layers together, and stamps the masks with nose strips, ear strings, and other pieces.
Completed face masks are then sent to a separate sterilization unit before being sent out of the factory.
Surgical Mask Tests
Once layered surgical face masks are made, they must be tested to ensure their safety in various situations. There are five tests they must be put through:
1. Bacteria filtration efficiency (BFE).
This test works by shooting an aerosol with staphylococcus aureus bacteria at the face mask at 28.3 liters per minute. This ensures the face mask can catch the percentage of bacteria it’s supposed to.
2. Particle Filtration Efficiency
Particle filtration efficiency or latex particle challenge is the test that involves spraying an aerosol of polystyrene microspheres to make sure the mask can filter the size of the particle it’s supposed to.
3. Breathing resistance.
To ensure the face mask will hold its shape and have proper ventilation while the person breathes, breathing resistance is tested by shooting a flow of air at it, then measuring the difference in air pressure on both sides of the face mask.
4. Splash resistance.
In splash resistance tests, face masks are splashed with simulated blood using forces similar to human blood pressure to ensure the liquid cannot penetrate and contaminate a person wearing the mask .
Since there are some substances in an operating room that can easily cause fire, layered surgical face masks are tested for flammability by being set on fire. It is set on fire to measure how slowly it catches and how long the material takes to burn.