Is the UV sterilization lamp completely sterilized?

UV radiation, as a mutagen, can cause abnormal chemical bonds between adjacent pyrimidine molecules in DNA or RNA in microbial cells such as bacteria and viruses within a specific wavelength range (mainly UVC 200-280 nm) and at sufficiently high doses, hindering the replication of DNA or RNA and causing microbial cell death.

The common ultraviolet sterilization and disinfection belongs to irradiation disinfection, which only requires shining the ultraviolet sterilization lamp on the items that need to be disinfected, or placing the ultraviolet sterilization lamp in the environment that needs sterilization and disinfection. Ultraviolet rays can concentrate high intensity to kill bacteria and viruses in a short period of time, and belong to pure physical disinfection methods without secondary pollution. So, how should the effectiveness of ultraviolet disinfection be determined compared to conventional chemical disinfection and heating disinfection?

The Disinfection Technical Specification (2019 Edition) by the Ministry of Health is one of the commonly used standards for evaluating the surface sterilization and disinfection effect of ultraviolet sterilization lamps. This standard verifies whether the bactericidal performance of ultraviolet lamps (including dual tube combination lamps) meets the qualified standards by measuring their irradiation intensity and bactericidal effect on microorganisms.

Radiation intensity

Ordinary or low ozone straight tube ultraviolet lamp (30W), the irradiance value of the new lamp tube should be ≥ 90 μ W/cm ²。 The irradiance value of the lamp tube in use should be ≥ 70 μ W/cm ²。 The measurement method and qualification standards for multi tube combined lamps are the same as those for single tube lamps. The detection distance and irradiance standards for special-shaped (non straight tube), high-strength, or non 30W power lamps are determined by the product's purpose and usage method. In principle, the irradiance value should not be lower than the one indicated in the product manual, and sterilization tests should be conducted according to the recommended dose [i.e. irradiance value multiplied by irradiation time (s)]. If it is proven that it can meet the required effects for application, it can be judged as qualified in laboratory testing. At the same time, 10 tubes were randomly selected for each identification of irradiation intensity testing, and each tube was tested three times. Only when all data meet the standards can the irradiation intensity be judged as qualified.

Microbial killing effect

Evaluation of bacterial strains: Staphylococcus aureus (ATCC 6538), Escherichia coli (8099), Pseudomonas aeruginosa (ATCC 15442), Bacillus subtilis black variant (ATCC 9372) spores and other bacteria, as well as their spores and fungi.

When determining the efficacy of microbial killing, the bacteria, their spores, and fungal tablets are first prepared according to the technical specifications, and then irradiated at the designated irradiation position. The irradiation is divided into three time groups, and the time settings of each group should enable the minimum dose required to kill the experimental bacteria, their spores, and fungi with a logarithm value of ≥ 3.00 to be measured. The determination of viable bacterial culture count of the irradiated samples is completed.