During the COVID-19 pandemic, face masks became a widespread public health tool. Their primary function is to act as a physical barrier, helping to reduce the transmission of respiratory viruses. By covering the nose and mouth, masks can intercept the respiratory droplets that are expelled when a person talks, coughs, or sneezes.
How Masks Prevent Transmission
Face masks reduce the spread of respiratory viruses through two main principles: source control and filtration. Source control focuses on preventing the wearer from spreading infectious particles to others. When an infected person exhales or coughs, a mask traps a significant portion of these particles before they can disperse, which is important as transmission can occur from people without symptoms.
The second principle is filtration, which offers protection to the person wearing the mask. The mask’s materials act as a filter, capturing incoming virus-containing particles from the air and reducing the amount the wearer inhales. The effectiveness of this filtration depends on the material’s properties and the size of the particles.
Types of Face Masks and Respirators
Respirators, such as N95s and KN95s, are a specialized category of face covering. These devices are constructed from multiple layers of synthetic polymer fibers, like polypropylene, which create a dense web of nonwoven material. This construction includes an electrostatic charge applied to the filter media, which helps to attract and trap airborne particles. These masks are made to form a tight seal against the face.
Surgical masks are another common type of disposable face covering. These are loose-fitting and made from a combination of paper and plastics. Their construction usually involves multiple layers, with a fluid-repellent outer layer and an absorbent inner layer. They are primarily intended to block large-particle droplets and splatters from reaching the wearer’s mouth and nose and also serve as source control.
Cloth masks represent the most variable category of face coverings. They can be made from a wide range of fabrics, such as cotton or hemp, and differ greatly in their construction. The effectiveness of a cloth mask depends heavily on the type of fabric used, the tightness of the weave, and the number of layers. Some designs include a pocket for an additional filter insert to improve performance.
Comparing Mask Effectiveness
A clear hierarchy of protection exists among the different types of masks, with respirators offering the highest level of filtration. N95 respirators, when properly fitted, are rated to block at least 95% of airborne particles as small as 0.3 microns. Their performance is due to both the advanced filtration material and their ability to form a tight seal around the nose and mouth, which minimizes air leakage.
Surgical masks offer a moderate level of protection. While their material can be effective at filtering particles, their loose-fitting design allows for gaps around the sides, which can let unfiltered air in and out. Research indicates that surgical masks with ties can provide better filtration than those with ear loops because they can be secured more tightly. Their real-world effectiveness is often lower than their high laboratory-tested filtration efficiency due to these fit issues.
Cloth masks provide the lowest level of protection, though their effectiveness is highly dependent on their construction. A single layer of cotton fabric may block a small percentage of particles, while a multi-layered mask made of tightly woven fabric can be much more effective. Some studies have found that certain two-layer nylon masks with a filter insert can perform better than a basic surgical mask, and adding a filter can significantly increase filtration efficiency.
Proper Mask Usage and Fit
To get the most benefit from any mask, it must be worn correctly. A proper fit ensures that the mask fully covers the nose, mouth, and chin without leaving any large gaps on the sides or around the nose. The mask should be secured snugly against the face. For masks with a metal nose strip, this piece should be pressed down to conform to the shape of your nose.
A simple seal check can be performed to test the fit. After putting on the mask, place your hands over the surface and exhale forcefully. You should not feel any air escaping from the edges of the mask. For some respirators, you can perform a negative pressure check by inhaling sharply; the mask should pull tightly against your face if a good seal has been achieved.
Common mistakes can reduce a mask’s effectiveness. These include wearing the mask below the nose, leaving the chin exposed, or frequently touching the front of the mask while it is being worn. Ensuring the mask is worn consistently and correctly maximizes its protective capabilities.