Both microorganisms and viruses are germs; the difference is that the first ones are alive while the viruses are a sort of capsules with genetic material that reproduce themselves by replication in a living host. They can produce illnesses by killing, damaging, or changing the cells. The viruses are inactivated, rather than killed, by destroying their lipid capsule with detergent, soap, or a 70% alcohol solution.
Social distancing is among the best practices to avoid transmission of these germs since one of the mechanisms of spreading them is by direct contact with carrying people, by being at the reach of respiratory drops caused by sneezing or coughing. The use of face masks has proven to be useful for preventing people from breathing these drops or spread them around.
Although most viruses cannot be active long time over objects, it is not safe to touch surfaces that might be contaminated with germs since we could collect them and carry to our nose, mouth, or eyes, which a way of taking viruses into our body. Hand washing is an essential measure against the virus propagation, not only before having meals or after going to the bathroom but as often as possible after we touch objects and surfaces.
We are used to cleaning the objects and surfaces by removing dust, strange substances, and germs. This action does not necessarily kill microorganisms nor inactivate viruses but reduce the germs load by removing them. The proper use of disinfecting products might not give a clean appearance to the objects, but they will reduce the germs population. Getting down that population below a given safe standard is sanitizing, while sterilizing consists of eliminating them all, well the most that it is possible.
COVID-19 pandemic brought great interest in sanitizing items before touching them. There are several recommendations in the news and internet as well as products and devices for sanitizing items. Some consider the use of microwave ovens, maybe because they are widely available at home, they can heat, they are quick, or perhaps because of the resemblance of microwaves and irradiation, although not in the radioactive sense.
Microwave ovens are easy to load and operate so that it is reasonable to consider them as a possibility for sanitizing items. There are advices, some without the proper context, dealing with several objects: medical implements, protective masks, sink sponges, socks, postal mail, packages, and books. There are also reports of experiments conducted only to see what happens because it is easy to place objects that fit into the oven cavity.
Although one of the reasons that make the use of these ovens attractive is easiness, it is safeness the first issue to consider so that people using the apparatus does not get harmed. However, once that a method and procedure for heating, cooking, or eliminate viruses with microwaves, have been designed, the next step is the preparation of standard guidelines that include safety criteria. Then, effectiveness in performing the expected operation, and finally energetical and production efficiency.
Often, tests at home begin with easy experiments guided mostly by beliefs and internet advice that sometimes do not warn about dangerous conditions. Therefore, improvisation is not acceptable. Cooking and heating options described in the microwave ovens manuals, as well as the design of the apparatus itself, were studied and tested carefully so that these operations are safe and effective. The most appropriate conditions are also established for other substances or objects, known as microwavable, considering the oven features. Water is an essential ingredient for heating in a microwave oven because, without it, the substances or objects might either heat unevenly, having hot spots that might produce fire or not heat at all.
Concerning health issues, cooked meals are sanitized since the achieved temperature and the necessary time for preparing them are enough to eliminate germs. Regardless that one attractiveness of the microwave oven is the supposed heating rate, time is of great importance due to kinetic aspects.
Quickness could be a problem for microwave sanitizing since there are no guidelines for doing that in a kitchen oven. Many recommendations found on the internet do not consider the ratio water-power-time for assuring that the temperature in the system exceeds 80 °C, which is the suggested temperature to inactivate viruses as resistant as SARS-CoV-2 (COVID-19).
Electromagnetic waves in the frequency of the microwaves are not energetic enough to eliminate germs. This process is conducted by heating, and the susceptibility of the substances and objects for microwave heating must be evaluated in advance. We must be aware of the different materials that compose the objects, for instance, face masks decontamination is commented on the internet, but they are not just a piece of cloth. They have elastic bands and other parts that can be damaged. They might heat up unevenly despite they might not contain metallic parts and could not reach the decontamination temperature.
The most promising methods resemble the sanitizing of baby feeding supplies such as baby bottles, that could work for medicine syringes, cups, and spoons. General comments, mostly on the internet, could inspire or tempt people to consider any item that can be placed into the oven cavity as it was food. The modifications made to the kitchen ovens presented in journals like JMPEE were performed by researchers and engineers, who are experts that developed equipment and protocols accordingly to their specific experiments. We are obligated to warn people about the probable failure of simplistic procedures, which may be either risky or difficult to evaluate because confirming sanitization requires germ counting.
Universidad Autónoma de Nuevo León, Facultad de Ingeniería Mecánica y Eléctrica, San Nicolás de los Garza, Mexico
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