There are two kinds of masks used in hospital settings. Surgical masks, which mainly protect those around the wearer, and respirator masks, which also protect the wearer. These two categories of masks must meet different standards. Then there are non-medical fabric masks.
Surgical masks largely protect others – one-way rather than two-way protection. The are designed to protect patients.
In the US, surgical masks must conform to the ASTM F2100 standard. In the European Economic Area (EEA), surgical masks have to be certified through the CE marking process and conform to EN 14683 standards, and in China they must conform to Chinese standards, for example YY 0469, which covers masks with at least 95% particle resistance and at least 30% fluid resistance.
The protection offered by these masks varies. The standards allow for different levels of fluid and particle protection. They must however, meet a minimum standard.
If you are looking for solid two-way protection then you need a respirator mask.
There are broadly three standards for respirators. American N ratings, European FFP ratings and Chinese KN ratings. These letters are followed by numbers that indicate the level of filtration or the percentage of particles shielded.
Here are their respective filtering levels:
FFP1: at least 80%
FFP2: at least 94%
FFP3: at least 99%
N95: at least 95%
N99: at least 99%
KN95: at least 95%
KN99 at least 99%
To work fully, respirators need to be properly fitted. One way to test fit is to spray perfume and see it can be smelt.
FFP standards are issued by the European Committee for Standardisation, N standards are established by the American National Institute for Occupational Safety and Health (NIOSH) and KN standards are developed by the Chinese authorities. Mask maker 3M provides a useful guide comparing the three standards.
Understanding ratings helps. But knowing whether a product actually meets the standards marked on the packaging remains a challenge. A recent study suggests 70% of Chinese masks imported into the US fail to meet standards.
Masks made from fabric
Mask made from fabric are not used medically and therefore do not conform to the standards required for surgical and respirator masks. And there are no specific standards for them.
This does not mean they do nothing. However, it does mean their efficacy varies enormously.
Multiple layers of the right fabrics can make them more effective, so it is important to know what they are made from.
However, given how poorly many of them fit, even one that scores well on filtration, will do more to protect those around the wearer than the wearer.