This article is designed to understand the performance of a 20W power general straight tube UV disinfection lamp and to provide a reference for the use of 20 W UV disinfection lamps in medical institutions. Let’s read on!
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UV irradiation is a common method of disinfection, but currently, medical However, the UV lamps currently installed in medical institutions are of different sizes and are not used in a standardized manner. In order to understand the performance of 20W UV disinfection lamps and the proper use of 20W UV lamps in clinical use were systematically measured and In order to understand the performance of 20W UV lamps and the proper use of 20W UV lamps, systematic measurements of clinical disinfection lamps were conducted.
1 Method
1. UV disinfection lamp qualification standards
According to the National Standard GB 19258 of the People’s Republic of China, the new 20 W double-ended UVC germicidal lamp illumination is rated at 75 μW/cm² at 1 m distance. The initial irradiance of the new lamp should not be less than 93% of the rated value. Therefore, the initial intensity of the new 20 W lamp should be no less than 75 × 93% = 69.75 μW/cm². According to the 2002 edition of the Technical Specification for Disinfection, when the irradiation intensity of a UV lamp is reduced to less than 70% of the original intensity of a new lamp, it should be replaced in time. Therefore, the irradiance of a 20W UV lamp in normal use at a distance of 1 m should be at least 69.75 × 70% = 48.825μW/cm² to be qualified.
2. Selection of UV lamps
Firstly, 20 new unopened UVCA 20 W UV lamps were randomly selected to measure the irradiance of the new lamps. Secondly, from June 2013 to March 2014, 45 of the 245 20W UV lamps in use were selected to calculate the average hourly irradiance decay value and thus the service life. 45 UV lamps were selected to meet the following requirements: First, the first measurement irradiance value should be ≥55μW/cm². Second, the lamps should be used in strict accordance with the 2002 edition of the Disinfection Technical Specification after the test started, and the lamps should be turned on regularly for 1 h per day. Every 90 h of lamp use was measured in three phases. In addition, among the 245 of the 20 W lamps in use at the hospital, five 20 W lamps with an irradiance of 49 μW/cm² (critical value) at a distance of 1 m were identified and used for the sterilization test.
3. Monitoring method
According to the standardized monitoring methods provided by the Beijing Hospital Infection Quality Control and Improvement Center Expert group provided the standardized monitoring method. China Institute of Metrology SUV – 3 type ultraviolet irradiance meter was used for measurement. The irradiation meter was calibrated annually by the Beijing The irradiometer is calibrated annually by the Beijing Institute of Metrology and Inspection Science. According to the Ministry of Health The intensity of UV irradiation was measured according to the 2002 edition of “Disinfection Technical Specification” and the instruction manual of the irradiometer. The UV irradiation intensity was determined according to the Ministry of Health 2002 edition of the Technical Specifications for Disinfection and the instructions for the irradiometer. Each lamp is measured three times and averaged.
4. Calculation method
The irradiation intensity of the UV lamp gradually decreases during the use of the lamp. It is assumed that the irradiance of the 20 W UV lamp decreases at a uniform rate with the use time. The difference in irradiance was measured 4 times after each 90 h interval of use and calculated. The difference in irradiance is then divided by the corresponding time to obtain the average hourly irradiance decay value. The average time for the average irradiance of the new lamp to decay to 48.825 μW/cm² is calculated as the average service life of the 20W UV lamp. The formula is as follows:
- Difference in irradiance decay (μW/cm²) = irradiance value 1 – irradiance value 2 irradiance value2
- Average hourly decay rate (μW/cm²) = irradiance decay Difference ÷ Corresponding cumulative use time
- Average service life (h) = ( average irradiance of new lamp – 48.825) ÷ average hourly decay rate
5. Sterilization test
A 90 mm diameter Petri dish was used, and a standard strain of Staphylococcus aureus (ATCC 25923) was used for the bacteria. The bacterial suspension was firstly prepared with a 2-megawatt turbidity, and the bacteria were collected with a sterile quantitative spiking gun. 20 μl of the bacterial suspension was inoculated on a 90 mm plain nutrient dish, and the amount of bacteria was 1. 2 × 107 cfu/dish. A negative control dish was set up for each test. After irradiation, the results were observed after 48 h in a 35 °C incubator.
2 Results
1. the irradiation intensity of the new 20W UV lamp
According to the initial intensity value of not less than 69.75 μW/cm², the compliance rate of the 20 unused new lamps was 90%.
2. Average lifetime of clinical UV lamps
The initial intensity ratios of the 45 UV lamps are shown in Table 1. 45 UV lamps were measured in three stages of 90 h use. The average lifetime of 20 W UV lamps in our hospital was calculated to be 1,463 h. The average attenuation values of each phase are shown in Table 2.
Table 1 Intensity distribution of the tested 20 W UV lamps
| Lamp intensity (W) | Number of lamps | Composition ratio ( % ) |
|---|---|---|
| 55 ~ 60 | 2 | 4. 44 |
| 60. 1 ~ 65 | 7 | 15. 56 |
| 65. 1 ~ 70 | 18 | 40. 00 |
| 70. 1 ~ 75 | 13 | 28. 89 |
| >75 | 5 | 11. 11 |
| Total | 45 | 100. 00 |
Table 2 Average irradiance attenuation values per phase and service life
| Use time | Average hourly attenuation ( μW/cm² ) | Average life ( h) |
|---|---|---|
| Phase I | 0. 0189 | 1 385 |
| Phase II | 0. 0168 | 1 559 |
| Phase III | 0. 0181 | 1 447 |
| Average | 0. 0179 | 1 463 |
3. Critical UVC lamp direct sterilization test
A 20 W UVC lamp (49 μW/cm² at a distance of 1 m) was used to directly irradiate a 9 cm ordinary dish inoculated with a standard S. aureus strain at a distance of 1 m for 43 min, and was able to sterilize 100% of the standard S. aureus strain at 1. 2 × 107 cfu/dish.
3 Discussion
According to the GB 19258 standard, the initial intensity value of a new 20 W UVC germicidal lamp at a distance of 1 m should be no less than 69.75 μW/cm². Under this standard, we measured a 90% pass rate for the 20 new tubes. However, in actual clinical use, the irradiance of new lamps can be reduced by the current stability of the output, transformer type mismatch, transformer aging, voltage stability, and other factors. Therefore, the first measurement of 20 W UV disinfection lamp new lamp, intensity ≥ 60 μW/cm² is qualified. In accordance with this standard, we sampled 20 new UV lamps can all be used normally.
The intensity of 20 W UV disinfection lamps reduced to 70% of the intensity of the new lamp is 48. 825 μW/cm², so the standard for 20 W UV lamps in use should be set at ≥ 48. 8 μW/cm². The average service life of the 45 UV lamps measured was 1463 h, which is longer than the reported average service life of 30 W UV lamps 1138 h.
The intensity of 20 W UV lamps in use should be measured every six months in daily clinical work. There is no chemical indicator card for 20 W UV intensity exposure, and the irradiance of 20 W UV lamps must be measured using a UV lamp irradiance meter. The lamp should be replaced immediately when the intensity is measured to be less than 48.8 μW/cm². The average lifetime of 1,463 h suggests that the frequency of monitoring should be increased after 1,000 h of use of the 20 W lamp in order not to affect the sterilization effect.
The sterilization effect of UVC is determined by the dose of irradiation received by the microorganism. The irradiation dose = irradiation time (s) × intensity (μW/cm²). The higher the irradiation dose, the higher the disinfection efficiency. Therefore, the use of 20 W UV lamps for disinfection of the medical environment should be in accordance with the Technical Specification for Disinfection of Medical Institutions, which states that the lamp should be suspended at a height of 1.8 m to 2.2 m from the ground, with an intensity of ≥1.5 W/m² and an irradiation time of ≥30 min.
The cleanliness of the UV lamp surface affects the disinfection effect, and the UV lamp should be wiped regularly with alcohol for a comprehensive wipe. If the number of UV lamps is insufficient, you can measure the irradiance value and then calculate the length of irradiation according to the formula, by extending the irradiation time can achieve the same sterilization effect.
References
[1] Application of two kinds of power straight tube UV disinfection lamps in hospitals [J]. Liu L. Chinese Journal of Hospital Infection. 2012(07)
[2] Quality management of ultraviolet disinfection in hospitals [J]. Liu Jimin, Li Li. Chinese Journal of Disinfection. 2012(01)
[3] Survey on the current situation of UV lamp use and its disinfection effect in medical laboratories [J]. Cao Jingyi. Chinese Journal of Disinfection. 2010(06)
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