Mask efficacy refers to how well a mask performs in reducing the transmission of respiratory particles. This performance involves filtering airborne particles and limiting the spread of exhaled droplets, which is particularly relevant for controlling respiratory illnesses. The effectiveness of masks varies, with certain types offering greater protection than others. The overall benefit of mask-wearing depends on consistent and correct usage.
How Masks Function
Masks primarily function by creating a physical barrier that intercepts respiratory droplets and airborne particles, preventing them from reaching the wearer’s nose and mouth or from being expelled into the environment. This barrier effect is achieved through two main filtration mechanisms: mechanical and electrostatic. Mechanical filtration involves the physical trapping of particles within the mask’s fibers. The effectiveness of this method is influenced by the density and structure of the fabric, with tighter weaves trapping smaller particles more effectively.
Electrostatic filtration is another mechanism, utilizing charged fibers to attract and capture oppositely charged particles, including very small ones. This method is prominent in specialized masks like N95 respirators and is becoming more common in other mask types. Many masks combine both mechanical and electrostatic filtration to enhance their particle-capturing capabilities. Additionally, masks act as source control, blocking exhaled particles from an infected individual, reducing their spread to others.
Understanding Different Mask Types
Different mask types offer varying levels of protection based on their design and materials. N95 respirators are designed for a close facial fit and are highly efficient at filtering airborne particles. They are regulated by the National Institute for Occupational Safety and Health (NIOSH) and must filter at least 95% of airborne particles as small as 0.3 microns. N95s offer superior filtration for both large and small particles, providing the highest level of protection among commonly available masks.
Surgical masks, also known as medical procedure masks, are loose-fitting, disposable devices intended to create a physical barrier against large-particle droplets, splashes, or sprays. They are typically made of three layers of non-woven fabric, with an inner and outer layer for fluid absorption and repulsion, and a middle filter layer. While surgical masks are effective at blocking large droplets, they are not designed to filter very small airborne particles as efficiently as N95s.
Cloth masks, often made from cotton or other fabrics, offer less protection compared to N95 or surgical masks. Their filtration efficiency varies widely, depending on factors like the number of layers and fabric type. For instance, their efficiency for submicron particles can be below 50%. While they provide some protection against larger droplets, they are not considered adequate for healthcare settings.
Variables Affecting Mask Protection
Beyond the mask type, several variables influence a mask’s protective capabilities. Mask fit is a primary factor, as gaps or poor seals between the mask and face allow unfiltered air to bypass the material. Even a highly efficient mask will have reduced effectiveness if it does not form a tight seal.
Material quality and the number of layers also play a substantial role, particularly for cloth masks. Masks with multiple layers, especially those incorporating a filter layer, offer improved filtration efficiency. Adding a filter layer to two cotton or non-woven fabric layers can significantly enhance filtration.
Humidity
Environmental factors, such as humidity, can also impact mask performance. Cotton masks, being hydrophilic, absorb moisture from exhaled breath, causing microscopic particles to grow larger and become more easily trapped. This increases their filtration efficiency in humid conditions. Conversely, synthetic fabrics, which are hydrophobic, do not show this improvement.
Particle Size
Particle size is another consideration. Masks perform differently depending on particle size, with some designs more effective against larger droplets and others for smaller aerosols.
Correct Mask Usage
To maximize mask protection, proper usage is as important as the mask’s inherent filtration capabilities. Before touching a clean mask, wash hands thoroughly with soap and water for at least 20 seconds. When donning the mask, ensure it covers both the nose and mouth completely, and adjust the nose piece to fit snugly around the bridge of the nose to minimize gaps. The mask should fit securely under the chin.
During wear, avoid touching the front surface of the mask, as this area may be contaminated. If the mask needs adjustment, use the ear loops or ties. When removing the mask, avoid touching the front surface; instead, use the elastic headpieces or ties to pull it away from your face.
After removal, dispose of single-use masks in an appropriate waste receptacle. Reusable cloth masks should be cleaned according to manufacturer instructions, typically by washing. Following mask removal and disposal or cleaning, perform hand hygiene again.