How we use the UVC lamp ?

After experiencing the "covid-19" epidemic, you are not your own personal hygiene, family hygiene are more important.

UVC germicidal disinfection lamp has the ability to sterilize, sold out everywhere, in addition to professional hospitals, but also a large number of companies and families snapped up for masks, drinking fountains, air conditioners and daily necessities, etc. UVC can effectively kill the "new crown" has been undoubtedly, but people still urgently need to popularize the knowledge of UVC germicidal The dose and measurement is the key.

Germicidal UVC

Knock on the blackboard, only UVC in the UVC can sterilize

Often heard "more sunshine, sterilization!" Is this true?

The answer is: true.

In other words, it is the sunlight that kills viruses and bacteria by heating them up. It is easy to understand that the SARS virus that ravaged 13 years ago suddenly disappeared in the summer because it was temperature sensitive!

Spectrum of light

So does UVC have disinfection and germicidal functions?

Yes, but only UVC has this skill.

As shown in the figure, UV radiation can be divided into UVA, UVB and UVC according to wavelength, where UVA has a strong penetrating ability, and most of the UV radiation received on the ground is UVA, and a small part is UVB, which has a weak penetrating ability, while the UVC component of sunlight is absorbed in the atmospheric ozone layer and cannot reach the ground, so it is customary to refer to the 200-280nm region of the sun's radiation that cannot reach the earth. Therefore, it is customary to call the mid-UV spectral region of 200~280nm, where solar radiation does not reach the earth, the "sun blind region".

Ultraviolet penetrating power

UVA and UVC irradiation of SARS virus survival in relation to irradiation time, UVA has almost no inactivation effect on SARS coronavirus, while under the characteristic wavelength of 254 nm, radiation intensity of 4016 μW/cm deep ultraviolet light source irradiation, virus killing rate LOG value and dose (time) is a linear relationship between the law.

UVC irradiation of bacteria, viruses and other microorganisms will destroy the molecular structure of DNA (deoxyribonucleic acid) or RNA (ribonucleic acid) in the cells of microbial organisms, causing DNA chain breakage, cross-linking rupture of nucleic acids and proteins, resulting in growth cell death and regenerative cell death, and achieving the effect of sterilization and disinfection.

UVC damages cellular DNA

UVC belongs to the broad-spectrum germicidal category, which can kill all microorganisms, including bacteria, tuberculosis, viruses, spores and fungi, but different disinfection objects require different doses.

Leaving the dose to talk about the effect is a hooligan

Germicidal UVC is not a new technology, and has long been used in the disinfection of indoor air, surfaces and water and other liquids. The effectiveness of UVC disinfection is related to the disinfection object (bacteria or virus type), the disinfection environment (water or air, temperature and humidity, flow and volume, etc.), as well as the radiation illumination (also known as "radiation intensity" in the medical field), radiation dose, and so on.

There is no how much UVC radiation dose should be to effectively kill the new coronavirus, but in 2003, Professor Dong Xiaoping's team pointed out that at a distance of 80cm from the germicidal lamp, radiation intensity greater than 90μW/c㎡, can effectively kill the virus in 60 minutes; in another study in 2004, the UVC light source close to the culture fluid to obtain a radiation intensity of 4016μW/cm2 In another study in 2004, a UVC light source was placed close to the culture medium to obtain a radiation intensity of 4016 μW/cm2 , which killed the virus more efficiently within minutes!

Compare this to heat disinfection, which takes 45 minutes to kill the SARS virus at 75 degrees Celsius, and 90 minutes at 56 and 65 degrees.

Duration of UVC disinfection at different temperature lines

This shows that UVC at sufficient doses to kill the new coronavirus is still very promising!

Two important physical quantities

Two physical quantities emerged just now when talking about radiation dose: radiation intensity and radiation dose.

Radiation intensity is what the medical community calls it. In the field of metrology, it is called radiation illuminance and refers to the radiation flux per unit area of the illuminated surface in watts per square meter (W/m2), usually written as μW/cm2.

Radiation illuminance

UV radiation dose is the UV energy received per unit area, is the integral value of UV radiation illumination and time, the unit is joules per square meter (J/㎡), usually written as mJ/㎡.

Relative to a certain UV radiation source, UV radiation intensity is not constant, usually gradually decreases with distance, as shown in the figure below.

Radiation intensity

When measuring the radiation illumination or radiation dose of UV extermination, it is necessary to clarify the location of the measuring instrument and the UV radiation source, and record the relationship between the radiation illumination and the change of time (if the radiation source is unstable).

Do not disinfect directly against the skin with UV light

Do not think that UV has the function of sterilization directly to their own disinfection, know that UV radiation can also cause irreversible damage to the human eye or skin, the following figure is the UV damage spectral sensitivity curve.

Ultraviolet damage spectral light and dark curve

According to IEC62471 standard, the 254nm UVC radiation should be below 0.2μW/c㎡ to ensure long-term exposure safety, and short-term exposure to UVC radiation irradiance should not exceed 1.7μW/c㎡.

In the IEC 60335 household and similar use of electrical safety series of standards, the requirements of the equipment with UVC sterilization system, signs and warning terms must be clear, and in the description section to give the appropriate content, so as to avoid the danger.

How to accurately "measure" the "radiation" dose

Scientific and accurate measurement of the radiation dose of UV sterilization, for the killing of viruses, to protect their own safety is very important, UV radiation measurement is mainly used in the following scenarios.

● R&D design and verification of UV disinfection products.

● Quality control and product certification of UV disinfection products.

● Initial installation acceptance and long-term monitoring of UV extermination application sites.

Don't underestimate the UV radiation dose measurement, think it's just a simple comparison with the UV irradiance meter, believe me it's definitely a technical job!