The factors that affect the effect of ultraviolet disinfection and sterilization are: (1) Lamp usage time: The sterilization power of the UV lamp decreases with the increase of the usage time. Generally, the output power of the UV lamp after 100h use is the rated output power, and the lighting time when the UV lamp is turned on to 70% of the rated power is the average life. The average life span of domestic UV lamps is generally about 2000h. (2) Environmental conditions: Generally, the UV lamp has the best sterilization effect when the ambient temperature is 20℃ and the relative humidity is 40~60%. When the temperature is 0℃, its sterilization effect is less than 60%. (3) Irradiation distance: within 500mm from the center of the tube, the irradiation intensity is inversely proportional to the distance, and above 500mm, the irradiation intensity is approximately inversely proportional to the square of the distance. (4) Bacteria: Due to the different membrane structures and shapes of the bacteria, the sterilization effect of ultraviolet rays on the bacteria, that is, the sterilization rate, is also different. If the product of the irradiation intensity and the irradiation time is assumed to be the irradiation dose, when the required dose of Escherichia coli is 1, it takes about 1 to 3 for staphylococcus, tubercle bacillus and the like, and about subtilis and its spores and yeasts. It takes 4~8, and about 2-50 for molds. (5) Installation method: The penetration rate of ultraviolet rays is low, and it is greatly affected by shielding and installation methods. In a biological clean room, there are generally several installation methods for pendant lights, side lights, and ceiling lights, among which ceiling lights have the best sterilization effect. Due to the limitation of ultraviolet bactericidal effect and the destructive effect on the human body that may be caused during sterilization, the use of ultraviolet lamps to sterilize biological clean rooms is rarely used, and only individual rooms or partial sections such as dressing rooms, laundry rooms, etc. are used . At present, the most commonly used ultraviolet sterilization is the gas-phase circulation sterilization method combined with the HVAC system.
