Bacteria/viruses have a peak absorption of light waves at 250-270nm, and the absorbed UV light can destroy the structure of its genetic material DNA so that it dies or loses the ability to reproduce, to achieve the purpose of sterilization. UVC light is like a unique and powerful “light knife”, is a broad-spectrum sterilization method.
Ozone is a strong oxidant and the sterilization process is a biochemical oxidation reaction. o₃ sterilization has the following 3 forms.
Ozone can oxidize and decompose the enzymes needed for glucose inside bacteria, causing them to inactivate and die.
Directly interacting with bacteria and viruses, destroying their cell walls, DNA and RNA, causing damage to the metabolism of the bacteria and leading to their death.
To penetrate through the cell membrane and invade into the cell, acting on the lipoproteins of the outer membrane and the internal lipopolysaccharide, causing the bacteria to undergo permeability distortion and lysis.
There are low-pressure mercury lamps on the market and LED UV lamps.
Low-pressure mercury lamp is currently the mainstream product, life 8000 hours, the main wavelength is germicidal efficiency 253.7nm, radiation efficiency to single-ended 18W for example, in more than 23%, high power up to 30-40%, and the lamp power from 1W to 300W, can meet the needs of different use scenarios, light maintenance rate is high.
LED long life, the current low efficiency, about 3%, low power, in the milliwatt level mainly; the current mainstream wavelength is 275nm . Overall, LED UVC prospect is good, currently suitable for small space disinfection such as contact lens disinfection, other scenarios due to the cost performance is not advantageous, more suitable for professionals to use experimentally.
Second, choose the material
Take the mainstream product low-pressure mercury lamp as an example. Low-pressure mercury lamps on the market are quartz tubes and high boron glass two categories.
Need to make a choice of specific use scenarios. Such as disinfection boxes or warehouse goods disinfection, need to use with ozone. (Note: Since ozone is harmful to cultural relics/paintings, etc., you need to consult a professional before use.)
Space disinfection a square configuration 1W, high requirements can be a cubic configuration 1.5W, that is, the floor height of 3 meters, for example, each square meter needs 4.5 watts.
Consideration of dose
Pneumoconiosis coronavirus is similar in structure to SARS virus and is also sensitive to UV radiation, as reported by CCTV in late 2003: 30w UV lamp kills the virus in 30 minutes at a distance of 1 m. The UV illumination at 1 m is 90 µW/cm2. The dose is: 90X30X60=162,000 microwatts-sec/cm2 Illumination * time = UV energy value.
Illumination time calculation
Calculation: 30W wall-mounted germicidal lamp as an example, a certain distance measured under the UVC illumination for the divisor, the calculated value is the time required. For example, at 20 cm, the measured 1000 microwatts / cm2 (of course, its illumination distribution and the corresponding lamp location), the calculated irradiation time is 2.7 minutes. (Illuminance is inversely proportional to the square of the distance.)
One of the reasons why viruses are much harder to kill than bacteria is that the (volume) area of viruses (light is not the same as high temperature, taking into account the area factor) is much smaller than that of bacteria. For example, in the general experimental reference E. coli, the area is about 10 times larger than the average virus. Of course, there are also differences in their DNA/RNA and outer wall factors.
Radiation dose (recommended)
UV UVC 253.7nm: General disinfection: 10,000 µW-sec/cm2 Disinfection of high-risk viruses such as New Coronavirus: 100,000 µW-sec/cm2
Fifth, choose a formal manufacturer or brand
The more non-professional users, the more you should choose a manufacturer with professional values and a sense of social responsibility. The market is mixed, inferior products and even fake goods, the function of all-embracing best not to touch. The price is very low, but also respect and stay away. For unfamiliar manufacturers, you need to confirm their qualifications and the test reports of authoritative institutions.
In order to use the convenience, and improve security, give priority to products with remote control, timer, radar / infrared sensor.
4 UV lamp use precautions
During disinfection, people and pets, animals to leave the disinfection room, can not be directly irradiated to people, prolonged exposure to ultraviolet light will cause burns to the eyes and skin; can not look directly at the bright lamp with the naked eye to avoid eye redness and burns; at the same time the high-grade silk, leather, paintings, valuable collectibles, important souvenirs to protect the light;.
Open the window for 20 minutes after disinfection, and wait 60 minutes for the ozone to decompose before entering the room to open the window.
Lamps should be collected after the end of disinfection to avoid damage to sterilization and personal injury caused by children’s misuse.
Q: Can masks be reused after disinfection with UV+Ozone?
A: It can be done as an emergency solution in case there are really not enough masks. After ozone disinfection, there is the smell of ozone, which can be put in a ventilated place to let it eliminate naturally.
Q: How is the dose of UV and ozone calculated?
A: UV: 90μW.S/cm2 UV intensity, irradiation for 30 minutes Ozone: concentration at 20.3mg/cubic, action time >15 minutes.