Basic facts of viral transmission (including the Flu)
If a person is infected with Coronavirus, there are four basic ways to prevent spreading of the virus through breathing, talking and coughing.
In the above, the arrows show the direction of air flow from breathing and talking. Forward distances shown are approximations only. Blocked distances are scattered and short.
No protection- viruses can travel up to 6 ft. This is the reason for the 6 ft social distance rule. It is flawed as air movement from wind, air conditioning and heating blowing can extend virus travel. There are situations especially at checkout counters at stores where 6 ft separation between cashier and baggers and customer is almost always violated with average distances about 3 ft apart.
Face masks– block air flow from nose and mouth that shortens how far the viruses travel if the wearer is infected. This helps a lot, but the viruses only spread less far.
Hand block- rarely mentioned except for coughs. It can shorten viral spreading from talking but is rarely used.
Face shields– blocks air flow from the mouth sending it sideways, upwards and down and even backwards from curvature and corners. Air flow is weakened by hitting a solid shield and then scattered.
Protecting yourself from Coronavirus
When the 6 ft social distance rule is broken and viruses come at you. You are on the defensive. These are what can happen:
No protection- viruses can be inhaled and infect the eyes.
Face mask– Face masks do not protect the eyes and most have little or no value stopping the breathing in of viruses. Learn more here. The N-95 respirator grade is the only effective face mask, but don’t protect the eyes. They are meant to be replaced after each use and are in short supply. They must be rationed to medical people. They require special training to use. Beware there are 3 types of N-95 masks made by 3M. Only one is the real McCoy Respirator grade for viruses.
Face masks may create a false sense of security. They have little or no protection value for the wearer. The CDC has recently advised their use only to limit how far infected breath travels from those who don’t know they are infected. If a mask talking or breathing travels only 2-3 feet instead of up to 6 ft, this is much better than nothing.
Face masks that are easy to breathe through have openings that let in too much. Respirator N-95’s are tough to breathe through for that reason.
Hand block- there is a scattering of viruses, but they can be inhaled and infect the eyes.
Face Shield- virus air flow scatters up, down, right, left, and past the shield. There is minimal danger of breathing them in or getting them on eyes. It’s not 100% protection so trying to maintain 6ft social distance is still a good idea. The face shield is a great backup for intrusions into the 6ft social distances that are going to happen for various reasons. The most likely violations are paying for things at cash registers and walking down two-way isles in stores.
Always beware of aerosol mists or clouds of viruses when in confined spaces with others. If there is little air space and movement, an infected person can create a cloud of viruses. This would occur in something like a bedroom or car. Only respirator grade N-95 masks can handle this. Other masks are of little protective value to the wearer. Viruses in this case may get around a face shield. Beware of confined spaces with other people.
So the Coronavirus is a two-way street. Prevent spreading it and prevent getting it. The face shield is a powerful tool to be used with 6 ft social distances and constant washing hands. They also keep us from touching our lips, nose, and eyes.
You can test all 8 scenarios above by blowing cigarette smoke with each and watch where the simulated viruses the smoke goes.
All of the above scenarios assume air movement from a person, coughing, talking or breathing. There is another danger for inhaling coronaviruses. If an infected person is in an area with little or no air movement for some time, they can generate tiny infected droplets, tinier infected aerosols, and possibly just viruses floating like dust. If you walk into this cloud of viruses, you will probably breathe some in. Six-foot social distances, face masks and face shields are of little value in such an air mass.
Examples of this kind of situation are in a car or van, a small room, or an indoor area with a large number of people sitting or standing with little ventilation.