N95 masks in terms of micrometers

N95 masks, also known as N95 respirators, are a specific type of disposable face mask that is part of the PPE (personal protective equipment) in many work settings where workers are exposed to respiratory hazards. These are small particles that can affect the health of a person if they inhaled them during long periods.

The term ‘N95’ comes from the National Institute for Occupational Safety and Health, commonly referred to as NIOSH, which is a federal agency that was created in 1970 as a part of the Centers for Disease Control and Prevention (CDC). Their goal is to create recommendations and spread information that is based on scientific research and knowledge, to help prevent occupational injuries or illnesses.

As part of their job, they also created a classification and rating system for respirators, in which they name respirators according to two main characteristics: oil resistance and filtration efficacy. NIOSH tests and certifies whether or not a respirator meets the requirements for each respirator type inside their classification, and this is considered the respirator filtration standard in the United States.

Respirators are important devices in the PPE of workplaces like construction or mining sites where the workers are exposed to hazardous particles. Respirators prevent them from inhaling these particles, which get trapped on the filtering media they contain.

The NIOSH classification names respirators following this system:

The first part of the name is a letter, which can be either N, R, or P, and it indicates how resistant the respirator is to particles that contain oil, and this is directly proportional to how well they can filter them. N means the respirator isn’t resistant to oil, R means it’s somewhat resistant, and P means it’s oil-proof.

The second part of the name is a number, either 95, 99, or 100, that is the percentage of minimum particulate filtration efficacy. This represents the minimum number of airborne particles (those with a size of 0.3 micrometers) the respirator can effectively filter out.

This means that N95 masks can’t filter out particles with oil in them, and they filter out a minimum of 95% of the non-oil-based airborne particles in the air. Some examples of particles they can filter out include dust, coal smoke, allergens, pollen, and some microorganisms like the flu virus or the new coronavirus that has been the cause of the COVID-19 pandemic, the SARS-CoV-2.

To trap the particles, N95 masks have a filter media with multiple holes that need to be small enough to trap airborne particles. As we mentioned, these particles have a size of 0.3 micrometers. This means the holes would have to be smaller than that to do this.

But, N95 masks have to meet certain breathability requirements for NIOSH to approve them, and having holes that small could interfere with this. This is why many manufacturers combine the non-woven fabric with holes in them with other filtration mechanisms, to be able to increase the circumference of the holes. The most widely used method is electrostatic filtration, in which they add electrostatic charges to the material. The principle under which this method is based is that the charges will attract particles with the opposite charge, no matter the size, trapping them and preventing them from being inhaled.

N95 respirators have been the preferred choice of face mask when it comes to virus protection in healthcare settings during the pandemic. They offer antiviral properties that aren’t present in other options, like surgical masks, or reusable cloth masks, the latter not being recommended to be used in the medical field. In the USA, 3M is one of the most popular brands, with some of the most purchased 3M N95 masks being the 3M 8210 and the 3M 8511.

These masks are usually confused with KN95 masks, and even though they’re very similar beyond their names, they are not the same mask. KN95 masks are respirators that can filter out 95% of the non-oil-based airborne particles but are regulated under the Chinese filtration standard, not NIOSH. Likewise, under the European standard, the respirators considered equivalent to these two are the FFP2 respirators.

Why focus on the circumference of N95 masks?

The SARS-CoV-2 is the biggest threat to public health around the world at the moment. This virus is an airborne particle, and it’s important to know if the holes in the filter of N95 masks can trap this virus to know if they can protect against them. Based on the explanation above, you can understand why they can protect against the coronavirus.

COVID-19 is the disease caused by this virus, a new infectious respiratory illness that was first reported in December of last year. This virus can cause a very severe illness in certain groups of people that have risk factors associated with them. However, most cases are mild or asymptomatic, with common symptoms being dry cough, sore throat, and fever.  

Although the severe cases aren’t the majority, if too many people become infected at the same time, these cases are much more concerning, since healthcare centers can collapse. The main focus right now, for this reason, is to prevent the virus from being spread among the communities to protect the most vulnerable people to the virus. Until a vaccine is developed and distributed, the most powerful resource to achieve this is the use of face-coverings in public settings.

The CDC recommends the general public to wear reusable cloth masks, including kids over the age of 2 years old. This is because medical supplies like surgical masks, respirators, face shields, and gloves have been hard to find for sale during the majority of the year. It’s hard to buy these items in bulk or wholesale even through online stores, which is why they need to be prioritized for healthcare providers during the pandemic.

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