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COVID-19 ADVICE BY DR.HON: Reusing Masks by Home Sanitization

COVID-19 ADVICE BY DR.HON: Reusing Masks by Home Sanitization

by Dr. David T. Hon, founder and CEO of DAHON folding bikes
Masks are expensive and in short supply. Reusable ones would be desirable. But it is generally believed that water-based sanitizers like alcohol would compromise the porosity and effectiveness of the melt-blown fabrics in most masks. 
I want to propose here that proper Pasteurization (1) using some home appliance can inactivate all Covid-19 coronavirus in any mask models. Invented in the 19th century originally for wine and later extended to the widest array of foodstuff and applications, including laundry dryers for clothes (2). All germs and viruses are killed when properly pasteurized, according to innumerable reports.  
Including the Covid-19 as well? Yes!. Covid-19 is just one form of coronavirus, which, as a class, has been categorically pasteurized billions of times for over a centuryAccording to the (U.S. ) National Milk Producers Federation (NMPF) in March 2020pasteurized milk is free of Covid-19 (3). Scientific and authoritative! 
More specifically, viruses and bacteria thrive at low temperatures and quickly die at higher temperatures. (That is why humans go into high fever for days as a last resort against diseases when the immune system has failed). Pasteurization can in principle occur at temperatures as low as 50°C – if one waits for a couple of hours. The higher the temperature, though, the shorter would be the needed time. For foodstuff in mass production, the temperature is often 72°for only 15 seconds. Table 1 provides the temperature vs. time required in the time-tested process (4). We can pasteurize masks for longer times for safety margins.  
Table 1. Pasteurization time vs. temperature.
Table 1. Pasteurization time vs. temperature

Laundry dryers typically run between 55 to 65° C at maximum settings. Some run higher. Unless you know the exact temperature and apply the above Table 1, it is safe to set the dryer at maximum temperature for one hour. Masks will come out completely sanitized and smelling fresh as new, ready for another day! 

Kitchen oven can also work, but many do not go below 80°. Above that, many mask materials will be damaged. Ovens with temperatures below 80° are available if you search hard online. 

A hairdryer is certainly hot enough to kill viruses, but at the risk of overheating and destroying the mask as well. (I am designing a simple device to regulate a hairdryer’s temperature experienced by the masks. I will describe this inexpensive DIY contraption at a later time.)  

UV light, used in many commercial and domestic sanitizing cabinets, is effective against viruses and bacteria. Check the manual for required timing. However, unlike heat, limited penetration in some units may limit the number of masks treatable at a time. Some advanced laundry dryers also use UV light along with heat.

The common microwave oven, unfortunately, will not work, as viruses are too minute for the electromagnetic wavelengths. 

I hope citizens will save time and money, as well as exposure, by renewing masks at home to protect themselves and others. Hospitals and other institutions may also consider this practical proposition in general. But even the best theory needs testing. Some public agency institution should undertake direct verification of this as a high-yield investment! 

I welcome suggestions and questions by readers or audience. 

The author, Dr. David T. Hon, is a graduate of DBS, UC Berkeley and UCLA/USC (Material Physics), and a Governor of Amcham South China since 2001; he has over 350 patents in several fields.