​Over the last few days, we have all heard the terms “PPE”, “Face Masks”, “Shields”, “N95 Masks”.  If you work in the health care field, you have heard these terms and should be quite familiar with their use.  But, for everyone else, such terms are quite confusing, and sometimes scary.

Below is a brief description of these terms, so at least you will be able to follow the nationwide conversation.


PPE = Personal Protective Equipment

This phrase is a catch-all phrase referring to any piece of clothing, eye wear, mask, etc which provides protection for the health care worker.

Different types of PPE include “face masks”, “face shields”, gloves, gowns, to name a few.

When we use “goggles” at home to protect our eyes while using a hammer, the goggles are re-used.  Such purchases are not “one-time use”.   Many of us may have purchased eye goggles 5 or 10 years ago, and are used repeatedly, as long as they are not broken.

Unfortunately, in protecting ourselves from the Covid-19 virus, such protective gear are “ONE TIME USE”.

If a nurse or doctor needs to talk to or examine a patient, to avoid getting infected themselves, they will need to wear appropriate PPE.  As soon as the nurse or doctor completes the evaluation with that ONE patient, they need to REMOVE and THROW AWAY the PPE, after just ONE USE !!!  If they do not remove the PPE, there is a chance that the virus has attached onto the PPE surface, and when the health care worker goes to interact with the next patient, the virus now has a chance to spread to another patient.

Since these pieces of PPE equipment are being used at such a high rate, there is now a nationwide shortage of masks, shields, etc.

How does PPE prevent an infection?

The important point is that the Covid-19 virus “infects” when we breathe the virus into our lungs.  Remember, if we just touch the virus, and we wash our hands, the virus is killed, and we are NOT infected.  But, if we touch the virus, and then touch our face, we are now allowing the virus to be inhaled into our lungs, causing the infection.

In brief, to avoid getting infected, one must avoid touching our face and prevent the virus from getting into our lungs.  So, we must (1) protect our hands, and (2) protect our face.

For the health care worker, it is quite easy to protect our hands.  We wear gloves, touch a patient, and then replace the gloves before touching the next patient.  Most medical-grade gloves are NOT porous, which means the gloves do NOT have tiny holes to allow water, blood, liquids, or viruses from penetrating the gloves.

With no holes, the “virus” cannot go “thru” the gloves to attach onto your hands. If the glove has a nick or cut, the virus can “penetrate the glove” and attach onto your hands.  You must now wash your hands to kill the virus, else there is a chance of spreading the virus.

So, the best practice is to wear gloves when interacting with patients, then remove gloves, wash hands, and put on a new pair of gloves before interacting with the next patient.

Masks are a totally different situation.

When a health care worker wears a mask, he needs to be able to breath thru the mask.  Hence, masks are not “solid”, but rather they are porous.  They are usually made out of “fabric”, with tiny pores or holes, to allow air to pass thru the mask (allowing the health care worker to breathe).

The size of the “pores” vary in size depending on the type of mask used.  Before we discuss “pore size”, we need to understand the size of the virus.

Aerosols and droplets containing particles that are <100 μm (micrometers) in diameter are not visible to the naked eye. Health care workers may not be aware of the presence of such particles and these particles could be inhaled or could easily cross-contaminate work surfaces, materials, and equipment.

Infectious droplets are defined as larger infectious particles (>5 μm in diameter) that rapidly fall out of the air.  Such droplets are not usually dispersed through the air.  Once they fall “out of the air”, they land on a surface.  When one touches the surface, the infection can spread.  Such a spread can be prevented by wearing gloves, and changing gloves in-between patient contacts.

Infectious aerosols are small liquid or solid particles suspended in the air that contain infectious agents (such as what would happen after a sneeze or cough). These infectious particles can disperse throughout the environment and remain infective over a period of time and distance. These particles are of a size (<5 μm in diameter) that may be inhaled into the lower respiratory tract (i.e. lungs), leading to a lung infection.

The Covid-19 is approximately 0.5 to 1.0 μm (micrometers), and remains aerosolized, allowing the virus to be breathed into the lungs, causing an infection.

In order to prevent this aerosolized virus (0.5 – 1 μm in diameter) from entering your lungs, the mask must have a “pore” size which is smaller than the virus, so the virus cannot physically pass through the pores on the mask.

Types of masks

The most commonly available masks are “surgical masks”.  These can purchased on Amazon, pharmacies, department stores, etc.  There is absolutely NO standardized guidance for the “pore size” for these masks.  Typically, the pore size of such surgical masks range from 25 μm to 150 μm.  So, if you buy the “best” surgical mask, the pore size is more than 50-100 times larger than the size of the virus (since the virus is approximately 0.5 to 1.0 μm).  Such a mask is totally useless in preventing the entrance of the Covid-19 virus into your lungs !!!  You may “feel” safe wearing such a mask, but once you understand the science, you will quickly realize that such masks are a waste of money and giving you a false sense of security.

In contrast, an N95 mask as a pore size of 0.3 μm !!  It is so small, that the Covid-19 is not allowed to pass through the mask, while still allowing oxygen and air to pass through, allowing you to breathe safely.

So, please do NOT hoard these N95 masks.  Please allow the health care workers to purchase and use these masks.  They need these masks to help keep you safe.

Stay safe !

  •  Sudhir S. Athni, MD


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