The Occupational Safety and Health Administration, commonly referred to as OSHA, is an organization inside the United States that has the job and responsibility to ensure all work environments inside the country are safe for their workers through the implementation of standards and regulations. This gives them the authority to define what a filtering facepiece respirator, or FFR, is. Their definition says that an FFR is “a negative pressure particulate respirator with a filter as an integral part of the facepiece or with the entire facepiece composed of the filtering medium.”
Let's break up this definition into two parts. The first part tells us that an FFR is any type of respirator in which the whole facepiece (that is, the mask itself) is made with the filtering media, or if the filtering media is an integral part of it. This means that the filtering part of the respirator isn't separate from the mask, like in respirators with valves and filtering cartridges, in which the only part that filters out air is the valve or the cartridge.
The second part of the definition given by OSHA tells us that the respirator must be a negative pressure respirator, and this means that the air on the inner side of the face mask must have a negative pressure in comparison to the air pressure on the outer side of the respirator. This negative pressure is created by the wearer when they inhale, and it ensures that all the air that is being inhaled is going through the filter on the mask, and therefore no harmful particle is entering the airway.
N95 masks are considered to be FFRs since they're made out of multiple layers of filtering media stacked on top of each other. The filter media used on most N95 masks is a non-woven fabric made out of polypropylene, a plastic with many uses in many different industries and products. To create the non-woven material, also known as non-woven fabric, polypropylene is put through mechanical, thermic, or chemical forces that leave a fabric with multiple small holes in it as a result.
These little holes are the filtering part of the material since they’re small enough to trap airborne particles in the air, but to ensure better breathability for the respirator, manufacturers make the holes not as small and add electrostatic charges to the filter media. The principle of this method is to trap the particles, both large and small, with the opposite charges. This combination of filtering methods ensures both a good filtration efficacy and breathability.
N95 masks are a type of respirator inside the classification established by the National Institute for Occupational Safety and Health (NIOSH), a federal agency part of the Centers for Disease Control and Prevention (CDC) that is often confused with OSHA. However, NIOSH has the responsibility to spread information and recommendations that could help work settings inside the USA to be safe.
NIOSH regulates respirators because they’re a crucial part of the personal protective equipment in many work settings with respiratory hazards. These are particles that can be detrimental to the worker’s health when they inhale them both acutely or chronically. Some of the diseases that can be developed in this way include lung cancer or chronic obstructive pulmonary disease (COPD). Respirators prevent these diseases by filtering out those particles from the air and preventing them from entering the wearer’s airways while they work.
The classification established by NIOSH names respirators based on two characteristics, their resistance to oil, which represents how well they can filter out oil-based particles, and their filtration rate, which tells us the percentage of airborne particles from the air they can filter out. The first characteristic is indicated with a letter: N for not resistant, N for somewhat resistant, and P for oil-proof. The second part of the name is a number, which can be either 95, 99, or 100%.
N95 masks are, based on this, respirators that can filter out at least 95% of the non-oil-based airborne particles in the air the wearer is inhaling. Such particles include dust, coal smoke, and bioaerosols like the flu virus or the virus responsible for the COVID-19 pandemic. Particles that can't be filtered out by these masks include glycerin and cutting fluid because they contain oil, and gases and vapors because they're smaller than 0.3 micrometers.
For this reason, N95 masks have been considered during the COVID-19 pandemic to be the best disposable face mask for virus protection. The characteristics mentioned give them antiviral properties that can't be found in other face masks available at the moment, including surgical or medical masks. Some of the most sought out N95 masks are the 3M N95 masks, with popular models being the 3M 8511 and the 3M 8210. N95 masks can also be worn easily with face shields, a practice common among healthcare workers during the pandemic to protect the eyes as well.
KN95 masks, like the N95 masks, are considered FFRs, and are usually considered good substitutes for N95 masks. Their names get them confused all the time, and even though KN95 masks are regulated under the filtration standard used in China, they can substitute each other during emergencies. Especially during the COVID-19 pandemic, we’ve seen healthcare workers using KN95 masks because N95 masks have been scarce for the majority of the year.
The general public is urged to wear alternatives to these medical-grade face masks which need to be reserved for workers on the frontlines of the pandemic. The CDC recommends the general public to wear reusable cloth masks, which can be found for sale easily online to buy in bulk and wholesale, including masks in a smaller size for kids over the age of 2.