Ultraviolet (UV) disinfection lamps, also known as UV sterilization lamps or UV fluorescent lamps, are lighting fixtures that utilize the bactericidal effect of UV radiation for sterilization. These lamps emit UV radiation with a wavelength of 253.7nm, which has the strongest bactericidal ability and can be used for disinfection and sterilization of water, air, clothing, and more. Common specifications of UV disinfection lamps used in pig farms include 15W, 20W, 30W, and 40W, operating at a voltage of 220V. They are primarily used for personnel disinfection and sterilization, and are commonly installed in disinfection changing rooms, veterinary clinics, and laboratories. So, what are the factors that affect the disinfection effectiveness of UV disinfection lamps? Let's explore this knowledge with our photobiology editor.

1. Influence of voltage

     The radiation intensity of a UV light source is significantly influenced by voltage. For the same UV light source, when the voltage is insufficient, the radiation intensity decreases significantly. The radiation intensity of a 30W straight-tube quartz UV lamp under different voltages can be calculated using the following formula:

Y=1.287X-177.87

In the formula, Y represents the theoretical value of ultraviolet intensity, with the unit of uW/cm2;

X-voltage, unit: V.

   If the acceptance control point for new UV lamps is set at an intensity of 100 uW/cm2 at 220V, then the control line for measuring the radiation intensity of new UV lamps at different voltages is as follows:

Y= 1.287X-183.14

If the intensity of 70uW/cm2 at 220V is taken as the control point for replacing the old lamp, the radiation intensity control line measured at different voltages is

Y= 1.287X-213.14

2. The influence of distance

    Generally speaking, the radiation intensity of ultraviolet (UV) lamps is inversely proportional to the square of the distance. The radiation intensity Y of a 30W low-pressure mercury hot cathode straight tube lamp decreases exponentially as the distance x from the lamp increases. The exponential curve equation is

Y^= 102.885? 9-0.760? 8x

Based on this formula, the radiation intensity of ultraviolet lamps at different distances can be calculated.

3. Impact of temperature

     The impact of temperature on the effectiveness of ultraviolet (UV) disinfection is achieved by affecting the radiation intensity of UV light sources. Generally speaking, UV light sources emit the strongest bactericidal UV radiation at 40°C. As the temperature decreases, the output of UV lamps decreases. When the temperature is higher than 42°C, the reabsorption of UV radiation increases, and the output also decreases. Therefore, both excessively high and low temperatures are detrimental to UV disinfection. However, some sterilization experiments have shown that within the range of 5~37°C, temperature has little effect on the bactericidal effect of UV. At low temperatures, microorganisms become more sensitive to UV radiation.

4. The influence of relative humidity

    Relative humidity also affects the effectiveness of air disinfection. When the relative humidity (RH) is too high, the increase in small water droplets in the air can block ultraviolet rays. Therefore, it is recommended that the relative humidity be below 60% when using ultraviolet radiation for air disinfection. When disinfecting surfaces, if the irradiated surface is relatively far from the light source, the water particles in the air can also affect the disinfection effect.

5. The influence of irradiation time

   The disinfection effect of ultraviolet rays is exponentially related to the irradiation dose, which can be expressed as

N/No=e-Klt

In the formula, N0 represents the bacterial count before exposure;

N--The number of bacteria after a certain period of exposure;

t1 - exposure time;

- Irradiation intensity;

K-constant.

    From the above formula, it can be seen that increasing the irradiation time t or enhancing the irradiation intensity can both enhance the sterilization effect. The irradiation dose is the product of the irradiation intensity and the irradiation time. Therefore, to achieve a certain level of sterilization rate, a sufficient irradiation dose must be ensured. When the radiation intensity of the ultraviolet light source meets the requirements (greater than 40uW/cm2), the required irradiation dose can be achieved by adjusting the irradiation time.

6. Impact of protection of organic compounds

   When microorganisms are protected by organic matter, a higher irradiation dose is required because organic matter can affect the penetration of ultraviolet light into the interior of the microorganisms and may absorb ultraviolet light.

7. Impact of microbial species and quantity

Different microorganisms have varying levels of resistance to ultraviolet radiation, and the irradiation dose needs to be determined based on the type of microorganisms to be killed. The greater the amount of microorganisms contaminated on the items being disinfected, the worse the disinfection effect will be. Therefore, it is necessary to have a good understanding of the type and quantity of microorganisms contaminated on the disinfection target before disinfection, in order to determine the irradiation dose.