UV radiation is divided into three types.
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The Earth's atmosphere can completely absorb natural UVC radiation.
The Earth's atmosphere cannot fully absorb UVB radiation, allowing some of it to reach the Earth's surface.
The Earth's atmosphere can completely absorb UVC radiation, preventing it from reaching the Earth's surface.
What is Ultraviolet (UV) Radiation?
Ultraviolet (UV) radiation, known in Thai as "Rangsee Nuea Muang" (รังสีเหนือม่วง), is an electromagnetic wave emitted by the sun with a wavelength range of 100–400 nm. It is invisible to the naked eye. However, the reason we can see a blue glow in a room illuminated by a UV lamp is that ultraviolet radiation from the lamp interacts with fluorescent materials. These materials absorb some of the UV energy and then re-emit it at a lower frequency, within the visible spectrum. As a result, we perceive the light as a bluish or purplish glow.
How do UV-C 254nm and UV-C 222nm differ?
Many people may wonder how UV-C 254nm and UV-C 222nm differ. Let's first get to know UV-C 254nm. There is medical evidence showing that using ultraviolet-C (UV-C) radiation with a spectrum of 250-270 nm can eliminate viruses and bacteria that spread in the air. UV-C radiation has been used to disinfect in examination rooms, operating rooms, and medical equipment. The 254-nm spectrum is popular because it can be easily produced using mercury UV lamps and has a wavelength close to the range that provides the highest disinfection efficiency. The recommended duration for UV-C disinfection is at least 30 minutes. However, it is important to note that during disinfection, no personnel should be present in the room, and the room should be left unused for about 30 minutes after the disinfection process to ensure safety. This is because there is a risk of skin cancer and eye damage from exposure to UV-C radiation. The 254-nm spectrum can penetrate the skin and eyes.
Later on, UV-C radiation with a lower wavelength and dose (222-nm, dose 2 mJ/cm²) was introduced. This wavelength still maintains its effectiveness in killing germs, but it cannot penetrate the skin or eyes and is not harmful to human skin cells or corneas. This makes it safe for continuous use and exposure without posing a risk to human health.
