[Reading Science] Masks, Disinfected Using a Microwave?

On the 16th, as the morning temperature in Seoul dropped to minus 2 degrees Celsius, continuing the below-zero cold, office workers are heading to work wearing thick clothes and masks at the Sejongno intersection in Jongno-gu, Seoul. Photo by Kang Jin-hyung aymsdream@

[Asia Economy Reporter Kim Jong-hwa] The novel coronavirus infection (COVID-19) has made many people's daily lives exhausting, but it has also brought unexpected laughter.

Wearing masks to prevent droplet infection, washing hands frequently, and practicing social distancing by avoiding crowded places have become routine, thanks to the abundant information provided by health authorities and the media through various channels.

Recently, a story about Mr. A, who, after learning that the COVID-19 virus is 'vulnerable to heat,' put banknotes in a microwave to disinfect them and ended up burning the money, was introduced in the media, bringing laughter to many. However, besides Mr. A's case reported in the media, it turns out that quite a few people have tried to use microwaves to eliminate the virus.

Mr. A from Pohang, Gyeongbuk, decided to disinfect banknotes before using them and put 36 bills of 50,000 won notes (1.8 million won) in the microwave, but the banknotes got burned. When Mr. A visited the Bank of Korea to exchange them for new bills, he received only 950,000 won. Damaged banknotes are exchanged based on the remaining intact area: if 40-75% remains, half the amount is exchanged; if over 75%, the full amount is exchanged for new bills. So he recovered only about half.

Mr. B from Chuncheon, Gangwon, burned 20 bills of 50,000 won notes (1 million won) while disinfecting them in the microwave, but fortunately, only part was damaged, so he received the full amount back. Mr. C from Busan lost 60,000 won after putting 39 bills of 10,000 won notes in the microwave and burning them.

Since many people use banknotes together, they might have felt the need to disinfect them. However, as masks became difficult to obtain, quite a few people tried to disinfect them by putting them in microwaves. Most banknotes and masks end up burning when microwaved. Why do banknotes and masks burn inside microwaves?

Microwaves, which have become essential in our daily lives, generate electromagnetic waves called 'microwaves.' The water molecules in food absorb these microwaves and rotate vigorously, raising the food's temperature. However, when using a microwave, you must always use dedicated containers.

Containers made of glass or ceramics that allow electromagnetic waves to pass through, or plastic containers specifically designed for microwave use, are allowed. The representative material that should not be used in microwaves is 'metal.' Stainless steel containers, aluminum foil, or wrapping with silver foil are all prohibited.

A banknote that was burnt after being put in and heated in a microwave.
[Photo by Bank of Korea]

These metallic materials reflect electromagnetic waves, preventing the food inside the container from heating. Especially around pointed or thin metal shapes, electromagnetic waves concentrate, causing the metal to heat quickly and sparks to occur. Since sparks inside the microwave can lead to household fires, this is quite dangerous.

Banknotes burn because they contain metal components. Banknotes have anti-counterfeiting features such as silver dotted lines, hidden lines, and holograms. Most of these use conductive materials containing metal, causing electromagnetic waves to concentrate on these parts and ignite them.

The same applies to masks. Masks have a metal wire inserted in the nose area for fixation. This metal wire increases the risk of ignition. Even if masks are hard to obtain, it is advisable not to try disinfecting them in the microwave for reuse. It is better to discard them decisively.

If you feel uneasy about banknotes, wouldn't washing your hands after touching them be sufficient? Instead of trying to disinfect the items you use, how about washing your hands one more time? If you touch any objects or elevator buttons, door handles, etc., when going out, washing your hands is better.

This content was produced with the assistance of AI translation services.