Particulate protective masks are devices that provide respiration protection for individuals who suffer from breathing ailments. However, the masks available in the market may not be certified by the FDA.
Mechanisms of particle filtration by the mask
Masks have multiple mechanical and electrostatic mechanisms that remove particles from the air. These mechanisms can be combined to create a mask that delivers the most effective level of protection.
The most common filtration mechanism is interception. This type of filtration captures larger particles and prevents them from penetrating the filter. It is a particularly useful mechanism for respirator masks. Interception is especially effective against ultra-fine particles.
Another mechanism is diffusion. This filtration mechanism works best on particles below 0.1 microns in size. It is also known as the "Brownian Diffusion" because it causes very small particles to wander across streamlines.
Other less common but more practical mechanisms include gravitational settling and inertia. These two forces have a less dramatic impact on smaller particles. However, the effects of these forces are still significant.
Filtration efficiency at different flow rates
There are many factors that affect the filtration efficiency of a particle protective mask at different flow rates. Some of the major parameters include face velocity, face shape, filter materials, loading time, and temperature. These factors can significantly affect a mask's filtration performance.
Particles entering a mask are usually on a nanometer scale. The size of these particles has a big effect on their adherence to the material used in the mask. For example, a mask with a filter made of polycarbonate would be more efficient at removing nanoparticles than a mask made of knitted fabric.
Another major factor affecting filtration is relative humidity. A higher concentration of humidity can reduce the amount of charge present on the fibers and particles, thus decreasing their filtration efficiency.
Filtration efficiency of noncertified surgical masks
Surgical masks are used to shield wearers from infectious droplets found in clinical environments. They are commonly made with three layers: an outer layer repels water and an inner layer absorbs moisture. Studies have shown that different types of masks have different advantages and disadvantages. In addition, studies have revealed that external factors, such as relative humidity, face velocity, and the charge state of the particle, influence the efficiency of masks.
Filtration efficiency of surgical masks depends on several factors, including the type of fiber, the packing density of the fiber, and the chemical composition of the mask filter. The American Society for Testing and Materials (ASTM) has developed standard tests for mask filtration. These tests have been conducted on various materials, including polyethylene, polypropylene, and fluorinated polymers.
