The Past And Present Life Of Ultraviolet Lamp Irradiation And Disinfection
Jan 15, 2022
Because the ultraviolet lamp is economical, practical, convenient and easy to operate, as a traditional method of air disinfection, ultraviolet is widely used in the consulting room, treatment room and disposal room of grass-roots hospitals. However, in the process of use, the grass-roots hospitals do not monitor the intensity of ultraviolet radiation. Moreover, in recent years, schools are also using ultraviolet lamps for classroom air disinfection, There are also many bad cases of eye, face and neck burns. Understanding the past and present life of ultraviolet lamp irradiation and disinfection can help you use it correctly.
Origin and principle of ultraviolet air disinfection
Origin of ultraviolet air disinfection. Early research began in the 1920s. It began to be used in the operating room of the hospital in 1936 and was first used in schools to control the transmission of rubella in 1937.
The wavelength of ultraviolet light. The wavelength range is 400-100 nm, which is divided into three bands: A, B and C. Among them, UV-C band (290-100nm) has sterilization ability, which is called disinfection UV. Ultraviolet sterilization lamp is a special electric light source that directly uses ultraviolet (central wavelength is 253.7 nm) to achieve the purpose of disinfection.
Ultraviolet lamp disinfection principle. Ultraviolet disinfection lamp is a low-pressure mercury lamp, which uses the ultraviolet light emitted by the intensification of low-pressure (< 10-2pa)="" mercury="" vapor="" to="" irradiate="" and="" disinfect.="" there="" are="" two="" main="" luminous="" spectral="" lines="" of="" ultraviolet="" disinfection="" lamp:="" 253.7nm="" wavelength="" and="" 185nm="" wavelength,="" and="" the="" peak="" wavelength="" is="" 253.7nm.="" these="" two="" wavelengths="" of="" ultraviolet="" rays="" can="" play="" a="" good="" role="" in="" sterilization.="" the="" former="" can="" directly="" act="" on="" the="" genetic="" material="" of="" biological="" cells,="" that="" is,="" dna,="" destroy="" dna="" and="" cause="" bacterial="" death,="" and="" has="" the="" function="" of="" decomposing="" ozone;="" the="" latter="" can="" produce="" ozone="" with="" strong="" oxidation="" by="" interacting="" with="" oxygen="" in="" the="" air,="" so="" as="" to="" kill="">
The difference between ultraviolet disinfection lamp and ordinary fluorescent lamp and energy-saving lamp is
The tubes of ordinary fluorescent lamps and energy{{0}}saving lamps are made of ordinary glass. Ultraviolet rays cannot be penetrated, and they emit visible light after being absorbed by phosphor; The lamp tube of ultraviolet disinfection lamp is made of ultraviolet transparent glass or quartz glass, and ultraviolet light can be transmitted through the glass tube wall. Ultraviolet lamp is a kind of incoherent light source. When two ultraviolet beams intersect, there will be no interference. The radiation intensity of any point in the space radiation field formed by multiple UV lamps meets the superposition principle. The ultraviolet radiation intensity of a certain point in the space is inversely proportional to the square of the distance from the ultraviolet lamp, so the disinfection effect of the ultraviolet lamp is mainly concentrated in the range of 1.0m.
Classification of ultraviolet lamp and technical requirements of ultraviolet lamp
According to the shape, it can be divided into three categories: double end lamp (represented by s), double end lamp (represented by D) and self ballasting lamp (represented by z).
According to whether it contains ozone or not, it can be divided into two types: containing ozone (represented by Y) and not containing ozone (represented by W) 5.
Technical requirements for ultraviolet lamps
It mainly standardizes the technical requirements in the following aspects: (1) requirements for medical electrical safety; (2) Product performance and safety requirements, mainly the requirements for ozone residue or leakage and UV exposure; (3) Health and safety indicators, increase the evaluation of disinfection effect; (4) Requirements for environmental test; (5) Improve the original test method.
Scope of application, method, intensity and disinfection time
Scope of application: it is applicable to the disinfection of indoor air without people. When there are people in the room, ultraviolet lamp should not be used for disinfection. Ultraviolet air disinfection can be divided into indoor hanging irradiation method, mobile direct irradiation method and air duct internal irradiation method. UV lamp (30W UV lamp, intensity > 70 at 1.0m) μ W/cm2, Greater than or equal to 1.5W/m3).
Ultraviolet lamp disinfection time. Irradiation time Greater than or equal to 30min. When the ultraviolet lamp disinfects the indoor air, the room should be kept clean and dry to reduce dust and water mist. When the temperature is < 20="" ℃="" or=""> 40 ℃, or the relative humidity is > 60 percent , the irradiation time should be extended appropriately.
Influencing factors of ultraviolet lamp disinfection
1. Impact of floating population
① The experimental study on the relationship between ultraviolet air disinfection time and disinfection effect variables by Lin Yingxue and others shows that there is no crowd in the dispensing room, and the bacterial content in the air immediately, {{0}}.5h and 1.0h after disinfection does not exceed the standard, while the bacterial infection in the flowing air of the crowd in the buffer room rises quickly.
② Yang Cuifang et al. "Discussion on the effective time of air disinfection". Before disinfection and 0.5, 2h and 6h after disinfection in the infectious ward, the air was sampled by plate sedimentation method, and the bacteria were counted after routine culture. It shows that air disinfection is effective. After disinfection, under the condition of air flow, the UV maintenance time is short.
③ Lu Lo had no statistical significance on the three air disinfection methods of ultraviolet ray, three oxygen disinfection machine and circulating air disinfection machine in the static state.
2. Influence of temperature and humidity
(1) Disinfect indoor air. It has radiation output in still air with an ambient temperature of 20 degree . When the air temperature is high or low, it will affect the heat exchange between the surface of the lamp and the air, and then affect the temperature field inside the lamp, reducing the radiation output. The air contains water vapor. Because water molecules can absorb ultraviolet rays, when the air humidity is high, it will weaken the penetration of ultraviolet rays and reduce the disinfection effect. When the humidity is 70 percent , 80 percent and 90 percent , the radiation intensity needs to be increased by 50 percent , 80 percent and 90 percent respectively to achieve the same effect.
(2) Disinfect the air in the air duct. When the air temperature is 24 degree , the flow rate is 0.472m/s and the relative humidity is in the range of 35-85 percent , the radiation intensity of UV lamp is inversely proportional to the moisture content of air.
Therefore, the power of UV lamp should be increased when the humidity is high. Air temperature and humidity affect the radiation output of UV lamp.
3. Influence of air velocity
(1) For indoor UV irradiation. The increase of air flow rate will strengthen the mixing of indoor air, increase the opportunity of microbial particles in the lower part of the room into the upper space, and improve the sterilization rate; But at the same time, when the air velocity is too high, the residence time of microbial particles in the effective ultraviolet irradiation range will be shortened, and the sterilization rate will be reduced.
(2) For the irradiation method in the air duct of central air conditioning. The increase of air flow rate will strengthen the cooling effect of UV lamp, reduce the internal temperature of lamp tube and reduce the radiation output.
4. Ballast effect
The reference ballast has a stable voltage / current ratio at the rated frequency and is relatively unaffected by the changes of temperature, current and surrounding magnetic field. Tao Xidan and others found that the use of different ballasts has a great impact on the irradiation intensity of ultraviolet lamps. Therefore, in the daily supervision, the sensing and control personnel should strengthen the guidance on the correct use of ultraviolet lamps in the Department and reduce the influence of ballast and other factors on the effect of ultraviolet disinfection.
5. Effect of ultraviolet combined with chemical disinfection
The results of a study of the lancet showed that for the terminal disinfection of high-risk ward, the disinfection method of standard chemical method plus ultraviolet light (UV-C) can significantly reduce the probability of infection with multidrug-resistant bacteria and Clostridium difficile in patients who re-enter the ward 13.
6. Ozone requirements
In the initial ozone production rate: the initial ozone production rate without ozone lamp shall be less than 0.05g / (kW · h). The initial ozone production rate with ozone lamp shall not be less than 80 percent of the nominal value.
Attention should be paid to safety in the use of ultraviolet disinfection lamp. For example, ozone residue or leakage exceeding a certain concentration (0.16mg/m3 according to GB / T 18883-2003 indoor air quality standard) will cause harm to human body, and too much ultraviolet exposure will lead to cataract and skin cancer. Therefore, pay attention to ventilation after disinfection.
Intensity monitoring
For the monitoring of ultraviolet radiation illuminance in use, the ultraviolet radiation illuminance with 253.7nm as the main wavelength per unit area measured at 1m from the normal line in the middle of the surface of the ultraviolet sterilization lamp tube without reflector, and the unit is UW / cm2.
Instrument method: after turning on the ultraviolet lamp for 5min, place the probe of the ultraviolet irradiator with the measuring wavelength of 253.7nm at the center of the vertical distance of 1m under the tested ultraviolet lamp. After the instrument is stable, the data shown is the irradiance value of the ultraviolet lamp.
Indicator card method: after turning on the UV lamp for 5min, place the indicator card at the vertical distance of 1m under the UV lamp, with the pattern side facing up, irradiate it for 1min, observe the color of the color block of the indicator card and compare it with the standard color block.
Because the ultraviolet irradiator needs to be calibrated every year, there is no indicator card, which is simple and convenient to use. Therefore, most medical structures use the indicator card method to monitor the intensity of ultraviolet radiation.
Disinfection effect monitoring (environmental microbiology monitoring)
1. Sampling method
① Plate exposure method is adopted for class II, III and IV environment. Indoor area Less than or equal to 30m2, set 3 inner, middle and outer diagonal points, and the inner and outer points shall be 1m away from the wall; If the indoor area is more than 30 m2, set 4 corners and 5 points in the center, and the point distribution part of the 4 corners shall be 1m away from the wall. Put ordinary nutrient agar plate（ Φ 90mm) place each sampling point, and the sampling height is 0.8m 1.5m from the ground; When sampling, open the plate cover and put it next to the plate. After exposure for the specified time (15min in in class II environment and 5min in in class III and IV environment), put the plate cover on the back cover and submit it for inspection in time.
② Place the test plate in a 36 degree ± 1 degree incubator for training for 48h, count the number of colonies, and isolate pathogenic microorganisms if necessary.
2. Monitoring results
(1) Class II environment. The total number of bacterial colonies in the air Less than or equal to 4cfu / (15min · 9cm diameter plate).
(2) Class III and IV environment. The total number of bacterial colonies in the air Less than or equal to 4cfu / (5min · 9cm diameter plate).
Maintenance and registration
An ultraviolet use register shall be established. The average service life of the ultraviolet lamp shall not be less than 5000 hours 5, and the irradiation and cumulative irradiation time shall be recorded. The service life of ultraviolet disinfection lamp is reduced from the intensity of the new lamp to 70 μ The time of W / cm2 (power Greater than or equal to 30W), or the time of reducing to 70 percent of the original new lamp intensity (power < 30w),="" shall="" not="" be="" less="" than="" 1000h="" [15].="" the="" surface="" of="" the="" ultraviolet="" lamp="" shall="" be="" kept="" clean="" and="" wiped="" with="" 75%="" ~="" 80%="" (volume="" ratio)="" ethanol="" cotton="" ball="" once="" a="" week.="" when="" dust="" and="" oil="" stain="" are="" found="" on="" the="" surface="" of="" the="" lamp="" tube,="" it="" shall="" be="" wiped="" in="">
Personal protection during UV use and monitoring
Attention should be paid to safety in the use of ultraviolet disinfection lamp. For example, ozone residue or leakage exceeding a certain concentration (0.16mg/m3 according to GB / T 18883-2003 indoor air quality standard) will cause harm to human body, and too much ultraviolet exposure will lead to cataract, skin cancer, etc. For UV protection, it is generally required that the user shall not be present when the UV lamp is used; Or for the product composed of ultraviolet lamp, the leaked ultraviolet light can not be seen visually from any angle outside the product. For ozone protection, if the ultraviolet lamp with low ozone is not used, it is generally required that personnel shall not enter the site during the use of the ultraviolet lamp, and can only enter after stopping the use and ventilation; The above situation does not exist when using low ozone ultraviolet lamps.
Personal protection during monitoring. Sunglasses prepared in advance during monitoring to prevent occupational acute electro-optic ophthalmia (ultraviolet keratoconjunctivitis). Wear gloves and long sleeved clothes to prevent skin exposure and dermatitis. The higher the UV intensity, the longer the irradiation time, and the faster the symptoms appear.
Hospitals are the places where pathogenic microorganisms and susceptible populations are concentrated. The microorganisms in the air mainly include bacteria, viruses and fungi. Pathogenic microorganisms can be transmitted through air or aerosol, causing aggregation diseases such as tuberculosis, influenza, Aspergillus, and exposure to COVID-19 in a long time in closed environment. Good indoor air environment is an effective way to prevent the pollution of these pathogenic microorganisms, and safe and reasonable air disinfection is the main means to control the spread of air pollution. UV combined with chemical disinfection is conducive to the prevention and control of multidrug-resistant bacteria. For places where children study in school classrooms, ultraviolet disinfection in occupied rooms is not appropriate. Medical institutions or administrative departments should do a good job in publicity and education on the use of ultraviolet disinfection in school classrooms when no one is present, so as to prevent adverse consequences, or regular ventilation, a high-quality and low-cost air purification method to keep the air fresh. Ultraviolet disinfection should be used scientifically, not blindly, not excessively, and suitable for use.