Influencing Factors And Quality Control Measures Of UV Light Disinfection Effect On Microorganisms

UV light disinfection has the advantages of safety, convenience, economy, no residue, less damage to goods, etc. It is widely used in air, object surface, water and other It can kill pathogenic microorganisms within a few seconds and no harmful substances remain. Because of its economy, side effects, and ease of operation, it has a wide range of applications.

The sterilization effect of UVC is affected by a variety of factors, so it is important to find the influencing factors in the process of UVC disinfection and propose corresponding quality control measures to make it Therefore, it is important to find the factors affecting the disinfection process of UVC and propose corresponding quality control measures to make the disinfection more standardized and rationalized, to make the sterilization effect of microorganisms more complete and ensure the most effective irradiation and disinfection of UVC.

Let’s dive right in now, and you can click on the question that interest you,

1 The role of UV light disinfection

2 Influencing factors of UV light disinfection

3 UV disinfection QC measures

4 Discussion

UV light is a light wave invisible to the naked eye and exists in the outer part of the violet When UV radiation hits microorganisms, energy transfer and accumulation occurs. When UV radiation hits microorganisms, energy transfer and accumulation occurs, and the accumulation results in the inactivation of microorganisms, thus The accumulation results in the inactivation of microorganisms, thus achieving the purpose of disinfection. Ultraviolet disinfection is the use of ultraviolet lamp illumination The intensity of radiation emitted by the UV lamp is inversely proportional to the distance of the disinfected object. The distance of the disinfected object is inversely proportional. When the radiation intensity is certain, the longer and closer to the UV lamp, the better the disinfection effect, and vice versa, the worse. It can be used to disinfect surfaces or indoor air and is widely used in microbiological research, and It is widely used in microbiological research and production practice. In general laboratories, general hospital wards, operating rooms, and outpatient clinics in general laboratories, hospital wards, operating rooms, and outpatient treatment rooms. It can be used for disinfection in general laboratories, hospital wards, operating rooms, and outpatient clinics.

1 The role of UV light disinfection

Germicidal UVC radiation is used to destroy and change the DNA or RNA structure of microorganisms so that the bacteria die immediately or cannot reproduce to achieve the purpose of sterilization. The wavelength range of UVC is 15 to 300 nm, with the strongest germicidal effect of UVC at 260 nm. The strongest germicidal wavelength is around 260 nm. UVC lamps are artificially manufactured low-pressure mercury lamps, which can radiate a wavelength of mainly 253.7 nm UVC, with strong and stable germicidal ability. When bacteria and viruses absorb more than 3600~6500μw/cm dose, it is very destructive to bacteria and viruses. Bacteria, viruses have great destructive power, can make them lose their viability and reproduction, and then achieve sterilization effect. The higher the power of the UV lamp, the higher its effectiveness. The dose of UV radiation is the product of the irradiation intensity and irradiation time, and the disinfection and sterilization effect is enhanced with the increase of the irradiation dose. If the power of the UV lamp and the irradiation distance remain unchanged, the relative dose can be expressed in terms of irradiation time. UV radiation has different lethal doses for different microorganisms. According to the law of irradiation, the illumination is proportional to the light intensity of the light source and inversely proportional to the square of the distance.

2 Influencing factors of UV light disinfection

1) Ultraviolet light for air disinfection

The effect of UVC on air disinfection is influenced by temperature and humidity, and the appropriate temperature is 20-40 °C and the appropriate humidity is 40%-60%, which has been noted by many scholars. The temperature has the greatest effect on the germicidal rate of UVC, followed by the intensity of UVC irradiation.

2) UVC lamp irradiation intensity

New UVC lamp irradiation intensity should be greater than 100μw /cm2 (distance 1 m at), in use UVC lamp irradiation intensity should also be not less than 70μw /cm² (distance 1 m at). UV lamps should be 3 to 6 months with an ultraviolet radiation illuminance meter to do a radiation intensity test, to ensure a good disinfection effect.

3) The type of UV lamp, with or without reflector on the disinfection effect

It was reported that high boron UV lamps and quartz UV lamps were used to irradiate different species of bacteria were irradiated, and it was found that bacteria survived less under quartz glass tubes The number of bacteria that survived the irradiation of quartz glass tube UV lamps was low, while the number of bacteria that survived the irradiation of high boron glass tube UV lamps was low. UV lamps, so quartz glass UV lamps should be preferred lamps. The intensity of the new lamp should be measured under non-reflective conditions. The intensity of new lamps should be determined under non-reflective conditions. To facilitate the work, various reflector correction factors can be experimentally determined. The results measured with the reflector can be divided by the correction factor to obtain Without reflector intensity.

4) Placement of UV lamps and disinfection frequency

General air disinfection, every 10 m² hanging a 30w UV lamp is appropriate, hanging height generally does not exceed 2 m; with UV disinfection of the surface of the object, the distance between the lamp and the surface of the object is generally not more than 1 m, irradiation time of not less than 30 min. UV lamp placement is not reasonable, the formation of radiation frequency is not uniform, which can reduce the efficiency of UV sterilization. A reasonable disinfection frequency can guarantee the disinfection effect. Disinfection times Too frequent causes waste of resources, too few disinfection times will affect the disinfection effect.

5) UV lamp voltage used

UV radiation is affected by voltage is more obvious, the same UV source when the voltage is unstable, the radiation intensity is significantly reduced, the radiation intensity of the UV lamp increases with the increase in voltage.

6) Keep the lamp clean

The surface of the lamp should be kept clean, dust accumulation and dust can affect the disinfection effect of the UV lamp, the surface of the UV lamp should be wiped with 95% alcohol every month, wet mopping daily to reduce dust or install dust removal equipment.

7) Influence of temperature and humidity

Most pathogenic microorganisms are sensitive to UV radiation at low temperatures, but in general, the disinfection effect is better when the room temperature is in the range of 20 to 40℃. UVC radiation can destroy the conjugate relationship of bacterial macromolecules, this effect is easy to occur in the critical water content and water loss of bacteria, so the general high humidity conditions of UVC sterilization efficiency is low.

8) Types and numbers of pathogenic microorganisms

The sensitivity of different pathogenic microorganisms to UVC varies. In general, fungal spores have the strongest resistance to UV, followed by Bacterial spores, acid-resistant bacilli, viruses, and other bacterial propagules. In addition, more specifically, HIV is more tolerant to UV irradiation. The amount of exposure varies depending on the type of microorganism. The greater the number of microorganisms, the greater the dose required for disinfection. The higher the number of microorganisms, the higher the dose required for disinfection.

9) Disinfection object pollution degree and smoothness

UV is a low-energy electromagnetic radiation wave with weak penetrating power. The presence of organic matter can significantly affect UV disinfection efficacy. Disinfection objects rough surfaces or contaminants can affect the absorption of UV light and reduce the disinfection effect.

10) Dust and aerosol content in the air

When there are more dust and aerosol particles in the air, they will have a scattering effect on UV light and affect its disinfection effect.

11) Air velocity

Airflow rate also affects the disinfection effect of UV lamps. When the airflow rate increases, the cooling effect of the UV lamp is enhanced, the internal temperature of the lamp is reduced, and the radiation output is reduced. When the airflow rate is too high, it will shorten the time for microorganisms to particles in the effective UV irradiation range, resulting in lower disinfection The disinfection effect will be reduced.

3 UV disinfection QC measures

1)Selection of qualified UV lamps

In the purchase of UV lamps, pay attention to check the valid license. For example, CE certificate, etc.

2) Management of UV lamp installation

According to the requirements of the “Disinfection Technical Specification”, the lamp is installed in a suspended, mobile mode. The lamp frame is supplemented by a polished aluminum reflector, 1.5w /cm², object surface disinfection ＜1 m distance, disinfection effective area 1.5 ~ 2 m. Every 1 ~ 2 weeks with ethanol gauze or cotton balls to clean the lamp.

3)Improved operation methods

Add a metal reflector to the UV lamp, which can enhance the intensity of UV radiation.

4) Timely replacement of UV lamps

UV lamps with insufficient radiation intensity should be replaced in time. Usually, the germicidal effect of UVC is closely related to its radiation intensity and exposure time. In the standard range, the higher the radiation intensity of the UVC lamp, the better the germicidal effect, and vice versa, the lower the radiation intensity of the UVC lamp, the worse the killing effect. If the radiation intensity of the UVC lamp is slightly low, in the case of > 70μw /cm², the exposure time can be extended to compensate for the lack of germicidal effect. When the monitoring has proved that the radiation intensity of the UV lamp is lower than the specified standard value, the lamp must be replaced with a new one in time.

5) Implementation of the responsibility management system

To strengthen indoor cleaning and sanitation, items, countertops must be kept clean, at least once a week with 95% alcohol wipe the UV lamp. And timely replacement of radiation intensity lower than 70μw /cm² of the lamp.

6) Environmental factors

The sterilization effect of UVC lamps is obviously affected by environmental factors, with a general ambient temperature of 20-40 °C and relative humidity of 60%.

7) Management of UVC disinfection environment

Microorganisms attached in suspended dust particles than in aerosols have greater resistance to UV, dust particles in the air can absorb UV light. Under low-temperature conditions, most microorganisms are sensitive to UV light but will make UV disinfection less effective. Therefore, ventilation should be done regularly, every wet mopping daily to reduce dust or install dust removal equipment.

8) Procedure management of UV exposure concentration monitoring

Daily monitoring: Require the registration of lamp number, start time, daily irradiation start and end time, and accumulated time of irradiation after monitoring. After using the UV intensity monitoring card, do the analysis in time, and the accumulated use time should be <1000h.
Environmental control requirements for monitoring: The room temperature should be controlled at 20~25℃ and the humidity should be less than 60%.
On-site monitoring: The use of ultraviolet monitoring card for auxiliary light intensity monitoring, failure to immediately replace the ultraviolet lamp, biological indicators monitoring when available.
Ensure the accuracy of monitoring results: UV lamp and indicator card or auxiliary illumination meter intensity monitoring probe The induction window should be kept 1 m.

8) Strengthen the training of UV disinfection knowledge for medical and nursing staff

Pre-job training for new staff, requiring mastery of the correct UV disinfection principles, use methods and precautions, etc.

9) UV irradiation method

Since UV light can only kill microorganisms that are directly irradiated, the surface of the object should be directly irradiated by UV light when disinfecting the surface of the object, and sufficient irradiation dose should be achieved to ensure the disinfection effect of the UV lamp.

10) Measurement of UV lamp intensity

New lamps should be tested for intensity and should not be used if they are below 90μw/cm²; UV lamps in use should be tested at least 2 times a year for radiation intensity and should be replaced if they are below 70μw/cm². When testing the radiation intensity of UV lamps, we should take into account the room temperature, humidity and cleanliness of the lamps, preheating time, detection distance, detection time, and quality of the indicator card to avoid errors, and conduct regular testing of indoor air environment indicators so that problems can be found and solved in time.

11) Ensure disinfection effect

Each laboratory has a UV disinfection register, which contains the lamp usage time, daily disinfection time, and total disinfection time. Time, daily disinfection time, cumulative time, the signature of executor, intensity in The register should be carefully recorded after each disinfection.

4 Discussion

UV disinfection sterilization is a common method of disinfection of air and object surfaces in hospitals and microbiology laboratories, with the advantages of economy, practicality, convenience, simplicity, and good disinfection effect. It is an essential tool for disinfection in primary hospitals, but in its disinfection management, there is still insufficient awareness among primary medical staff and some safety hazards. The interference of the above-mentioned factors causes the disinfection effect of UV lamps to be greatly affected. Therefore, it is important to understand and master the influencing factors related to UV lamp disinfection, propose corresponding control measures and solve them, so that its management can be more scientific and reasonable and its effect more reliable. Therefore, effective link quality management is a significant measure to ensure the quality of UV disinfection and is also the key to ensuring the disinfection effect.

With the progress of science and technology, UVC sterilization technology is constantly developing. Especially in recent years, UV light sources such as high-pressure mercury lamps, induction lamps, and xenon lamps, etc. High efficiency, strong application of ultraviolet sterilization equipment has become a food processing plant and pharmaceutical plants with high factories and pharmaceutical plants and other places with high health requirements are indispensable to kill sterilization equipment. The application space for germicidal UVC is expanding greatly, especially The emergence of pulsed xenon lamp sterilizer has changed the traditional concept of using UVC to irradiate the surface of the emergence of pulsed xenon lamp germicidal apparatus, in particular, has changed the traditional concept of using UVC to sterilize the surface of objects. This provides a good idea of how to use UVC germicidal equipment in many areas.