A<unk> , also known by other names such as a medical face mask or procedure mask, is a personal protective equipment used by healthcare professionals that serves as a mechanical barrier that interferes with direct airflow in and out of respiratory orifices (i.e. nose and mouth). This helps reduce airborne transmission of pathogens and other aerosolized contaminants between the wearer and nearby people via respiratory droplets ejected when sneezing, coughing, forceful expiration or unintentionally spitting when talking, etc.<unk> s may be labeled as<unk> , isolation, dental or medical procedure masks. Although the material of which<unk> s are made will filter out some viruses and bacteria by trapping the aerosol suspended in breathed air, they only provide partial protection from airborne diseases because of the typically loose fit between the mask edges and the wearer's face.<unk> s are distinct from filtering respirators, such as those made to the American N95 standard, which are more airtight and purposefully designed to protect against finer airborne particles. Comparison of breathing out without (top) and with (bottom) a mask. Note that without a mask jets of air are exhaled that can carry viruses and bacteria rapidly towards a person in front of the person breathing out. But with a mask these jets are blocked, meaning the air instead mostly rises due to convection. Note that although jets are blocked, the same amount of air moves in both cases, allowing the wearer to breathe easily. Evidence from randomized controlled trials that<unk> s reduce infection from diseases such as influenza and COVID-19 is weak. Although a recent very large (over 300,000 people) study found some evidence that they reduced transmission in the community. However,<unk> s can vary greatly in quality which may make these studies less useful. The effect of<unk> s is partially attributed to filtering out some of aerosol particles that are how airborne diseases are transmitted.<unk> s are highly variable but the material of which they are made typically filter out more aerosol particles than do cloth masks but much less than does the material of which N95, FFP2 and similar masks, are made. This combined with the poor fit suggests that<unk> s offer some protection to airborne diseases such as COVID-19 but less than do N95, FFP2 and similar masks. There are standards for the materials masks are made from. For example, the European EN 14683 Type II standard requires the material of the mask to filter particles (mean diameter close to 3 micrometres) containing the bacterium Staphylococcus aureus. The bacterial filtration efficiency of the mask material is the fractional reduction in the number of colony-forming units (CFUs) when the aerosol is passed through the material. For a Type II mask under this standard, the material must filter enough of the aerosol particles containing the bacteria to achieve a CFU reduction of at least 98%. ASTM International has an F2100 standard with similar bacterial filtering standard to the European Type II standard but in addition uses a test aerosol of 0.1 micrometre particles. The Level 3 standard F2100 standard requires that these particles must be filtered out with at least 98% efficiency. Neither the European nor the ASTM standard tests performance as worn, they just test the material — the difference being the air leakage. This is different to personal protection equipment standards such as N95 and FFP, which do test performance as worn.<unk> s are made of a nonwoven fabric created using a melt blowing process. They came into use in the 1960s and largely replaced cloth facemasks in developed countries. The colored (usually dark blue, green, or occasionally yellow) side of the mask (fluid-repellant layer) is to be worn outwards, and the white side (absorbent layer) inwards. The use of<unk> s during the COVID-19 pandemic was a subject of debate, as mask shortage was a central issue.<unk> s are popularly worn by the general public all year round in East Asian countries like China, Japan and South Korea, especially during allergy and flu seasons, to reduce the chance of spreading airborne diseases to others, and to prevent the breathing in of airborne irritants such as pollens or dust particles created by air pollution (though dust masks are more effective against pollution). Additionally,<unk> s have become a fashion statement, particularly in contemporary East Asian culture bolstered by its popularity in Japanese and Korean pop culture which have a big impact on East Asian youth culture.
Surgical mask
Karman cannula
Venturi mask
Nasal cannula
Pocket mask
Gas mask
N95 respirator
Cloth face mask