The Editor,

Some thoughts on the effectiveness of masks in certain cases, and air conditioned spaces. First thought, a number of commercial face masks have outflow valves to make it easier to exhale; if you are using such a mask and you do not have COVID-19 that’s good.

However, if you have COVID-19 and are exhaling tiny droplets with the virus, that’s bad, because they are going, unimpeded out through the valve. So if there is even a tiny suspicion that you may have the virus, it might be far better to use a mask without the exhalation valve, or even a close fitting cloth mask.

Generally, masks help, but I wonder about our tear ducts. Ever notice that when your eyes are irritated and tears start flowing, they end up in your nose, having passed down through your tear ducts, possibly washing viral particles down your nose, not good. The use of eye protection, such as used in dusty environments, even because they are ventilated from the bottom should reduce your chances of catching the virus even more, because the viral particles would have to float upwards through the vent openings, highly unlikely.

So, a good, relatively cheap sort of protection against the virus would be the combination of a non-valved mask, and cheap safety glasses for dusty areas. The ultimate in protection (or against spreading the virus) would be a system where slightly pressurized filtered air flows over your face, and the out flow air is also filtered. Something, battery powered, like this is sold for welders and persons dealing with hazardous solvents, etc. but does not have the exhalation filter, but this could be added by the user if he is possibly infected.

I have thought for some time that most air conditioned spaces are not properly designed. With the advent of COVID-19 these spaces, especially mini-split systems without HEPA filtration (able to remove tiny particles and even viruses) could be just virus blowing in your face systems. I’m not sure mini-split units are even built to use HEPA filters.

With regards to the design of new centrally air conditioned spaces in the COVID-19 era, HEPA filters would be a necessity (to remove virus particles from the air), good fresh air addition as specified by ASHRAE (to flush out the system), powerful UV light sterilization in the duct work, overnight building sterilization, and careful airflow design so that, for example, in retail spaces the airflow would be crosswise between persons such as the customer and the cashier, and then to a filter so that neither one could get the virus.

 Buildings will have to be designed with far more care, almost like operating theaters for patientsd with infectious diseases.

Welcome to the 21

^st

century, the COVID-19 and other pandemic era.

 Regards

Howard Chin

 Member Jamaica Institution of Engineers

Registered Professional Engin