This paper combines the relevant regulations on UV disinfection in hospitals, focusing on the principles and types of UV disinfection, the design, installation, use, and distribution control of the UV lamp, and summarizes the design points and considerations for UV disinfection lamps in engineering design.
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1 Overview
At the end of 2019, the COVID-19 outbreak suddenly broke out, and in this epidemic prevention and control interdiction war, Wuhan Vulcan Mountain and Thunder God Mountain Hospital in China and Xiaotangshan Hospital renovation project in Beijing were quickly built and put into use within a short period of time, providing great help to the majority of patients and anti-epidemic work. The key to stopping the epidemic is to stop the spread of the virus, and it is especially important to disinfect and sterilize the limited space in the hospital.
Disinfection and sterilization methods commonly used in medical institutions: physical, chemical, and biological sterilization methods. The disinfection and sterilization methods commonly used in medical institutions are shown in Table 1.
Table 1 Common disinfection and sterilization methods in medical institutions
| Disinfection | Disinfection method | Specific methods |
|---|---|---|
| Physical methods | Thermal method (dry heat) | Burning, scorching, dry roasting |
| Thermal method (moist heat) | Steaming, pasteurization, flowing steam, Pressure steam sterilization | |
| Radiation method | Infrared disinfection, microwave disinfection, ultraviolet disinfection | |
| Chemical methods | Soaking method | Submerge items in disinfectant |
| Wiping method | Wipe contaminated items with a dressing soaked in disinfectant | |
| Spray method | Aerosolizing or spraying the disinfectant onto the surface of the object | |
| Fumigation method | Vaporizing or fuming the disinfectant by heating it | |
| Biocidal method | Use of biolysis of pathogenic bacteria to lyse and kill certain pathogenic bacteria |
Among the many methods of hospital disinfection, UV disinfection by radiation is used in hospital air disinfection and item disinfection and is a very effective means of virus disinfection. The purpose of this paper is to discuss how to make scientific and reasonable design and application of UV disinfection lamps in hospital buildings.
2 UV disinfection classification
UV disinfection mainly uses UV light with a wavelength of 253.7 nm (as shown in the figure) to disinfect microorganisms (bacteria, viruses, bacteriophages, and other pathogens) by damaging them through radiation.
Commonly used UV disinfection equipment can be divided into two types of UV disinfection lamps and UV disinfectors. UV disinfection lamps: special electric light sources that directly use UV light to achieve disinfection purposes, commonly used are hanging UV disinfection lamps, mobile UV lamps, UV disinfection cabinets, UV disinfection boxes, and many others. UV disinfection box is shown in the figure, and UV disinfection lamp is shown in the figure.
UVC sterilizer: a combination of UVC germicidal lamp, filter, and fan to achieve the purpose of disinfection of a device, its filter and fan does not have the role of sterilization factor, according to its appearance can be divided into wall-mounted sterilizer, cabinet sterilizer, mobile sterilizer, etc.
Disinfection by UV light can be broadly divided into two types: surface disinfection of articles and indoor air disinfection. Disinfection and indoor air disinfection. These two types of disinfection Both types of disinfection can be carried out using UV lamps and UV disinfectors. Table 2 provides a detailed analysis of the two types of disinfection combined with different disinfection equipment. Table 2 provides a detailed analysis of the two disinfection types with different disinfection equipment.
Table 2 Comparison of selected disinfection equipment for surface disinfection and indoor air disinfection
| Disinfection type | Disinfection equipment | Usage and characteristics |
|---|---|---|
| Surface disinfection of objects | Suspended or mobile UV lamps | The irradiation should be done when the room is unoccupied. Hanging 1. 8 ~ 2. 2 m from the ground; mobile Mobile type can be used flexibly by irradiating near and far |
| Ultraviolet disinfection box (ultraviolet disinfection cabinet) | limited space for disinfection of small items. Place items in the UV disinfection tank for disinfection | |
| Indoor air Disinfection | High-intensity ultraviolet air disinfector (fixed, Mobile type) | Can be used in occupied conditions with ozone-free UV lamp and UV leak prevention device to ensure its safety, continuous and dynamic disinfection |
| Suspended or mobile UV lamps | The irradiation should be done when the room is unoccupied. Hanging 1. 8 ~ 2. 2 m from the ground; mobile type can be used flexibly by irradiating near and far |
3 Design of hospital UV lamp
1) Design basis
At present, the existing codes in China have clear regulations on the places and areas that should be disinfected in medical buildings, as follows
a. JGJ 312 – 2013 Electrical Design Code for Medical Buildings, Article 8. 3. 5: UV disinfectors or UV disinfection lamps should be installed in waiting areas, infectious disease consultation rooms and wards, operating rooms, blood banks, decontamination rooms, disinfection supply rooms, morgues, garbage disposal stations, etc.
b. GB 50849 – 2014 “Infectious Disease Hospital Building Design Code”, Article 8. 2. 3: Germicidal lamps should be installed in clean corridors, washrooms, bathrooms, waiting rooms, consultation rooms, treatment rooms, wards, operating rooms and other places where sterilization and disinfection are required. Germicidal lamps and other lighting fixtures should be controlled by different switches, and their switches should be easy to identify and operate. Waiting room, corridors and other public places or usually people stay in the place of germicidal lamps, it is appropriate to use indirect lamps or irradiation angle can be adjusted lamps.
c. T / CECS 661 – 2020 “COVID-19 Infectious Pneumonia Emergency Medical Facility Design Standards”, Article 8. 0. 6: wards, buffer rooms, bathrooms, decontamination rooms, patient corridors and other places requiring sterilization and disinfection should be installed with fixed or mobile ultraviolet lamps and other disinfection facilities.
d. GB 15982 – 2012 Sanitary Standards for Hospital Disinfection has relevant standards for the disinfection of various environmental rooms, as shown in Table 3.
Table 3 Various types of environmental air, surfaces, and hands of health care workers Bacterial colony hygiene standards
| Environment Category | Scope | Air Standards (cfu/m³) | Object Surface Standards(cfu/m³) | Medical Staff Hand Standards(cfu/m³) |
|---|---|---|---|---|
| Class Ⅰ | Laminar flow clean operating room, Laminar flow clean ward | ≤ 10 | ≤ 5 | ≤ 5 |
| Class Ⅱ | General ward, delivery room, infant room, premature baby room, general protective isolation room, supply room sterile room, burn ward,intensive care unit | ≤ 200 | ≤ 5 | ≤ 5 |
| Class Ⅲ | Pediatric wards, obstetrics and gynecology examination rooms, injection rooms,drug change rooms, treatment room, supply room cleaning area, emergency room, laboratory, All kinds of general wards and rooms | ≤ 500 | ≤ 10 | ≤ 10 |
| Class Ⅳ | Infectious disease department and wards | — | ≤ 15 | ≤ 15 |
2) UV disinfection conditions of use
UV disinfection lamps are used at a relative humidity of < 60 % and a temperature of 20 ~ 25 °C. UV disinfectors are used at a relative humidity of < 80 % and a temperature of 5 ~ 40 °C.
3) Design of UV disinfection
A. Object surface disinfection
Object surface disinfection is usually done by direct irradiation, with a certain UV radiation irradiation for a certain period of time to achieve the disinfection effect.
*UVC radiation illuminance E
UVC radiation illuminance E is a specific distance (usually 1 m) from the surface of the germicidal UVC lamp, measured per unit area of UVC radiation illuminance, which can also be calculated using the following method.
E = dΦ / dA
Where: E – radiation illuminance of the UV lamp, µW / cm²; dΦ – radiation flux of the UV lamp on the surface element at a given point, W; dA – area of the surface element at a given point at a certain distance from the UV lamp, cm².
Double-ended lamp and single-ended lamp initial UV radiation illumination shall not be less than 93% of the value specified in Table 4 and Table 5, respectively.
Table 4 Double-ended lamp UV radiation illuminance table
| Nominal power / W | 4 | 6 | 8 | 13 |
|---|---|---|---|---|
| UV radiation illuminance of double-ended lamps / (µW / cm²) | 11 | 17 | 22 | 35 |
| Column 1 Value 2 | ||||
| Column 1 Value 3 | ||||
| Column 1 Value 4 |
Table 5 Single-ended lamp UV radiation illuminance table
| Nominal power / W | 7 | 9 | 11 | 18 | 24 | 36 | 55(T5) | Column 9 |
|---|---|---|---|---|---|---|---|---|
| UV radiation illuminance of single-ended lamps / (µW / cm²) | 18 | 28 | 40 | 52 | 100 | 150 | 185 | Column 9 Value |
*Ultraviolet radiation efficiency η
UV radiation efficiency η is the ratio of the initial UV radiation flux of the UV lamp to the actual input electrical power, expressed as a percentage, calculated as follows.
η = Φ / P
where: η – UV radiation efficiency. Φ — the initial UV radiation flux of the UV lamp, W. P – the actual input electrical power of the UV lamp, W. Double-ended lamp, and single-ended lamp initial UV radiation efficiency should not be lower than Table 6, the UV radiation efficiency of self-ballasted lamps should be no less than 85% of the specified value for single-ended lamps. The UV radiation efficiency of self-ballasted lamps should be no less than 85% of the specified value for single-ended lamps.
The values in Table 6 are all double-tube type parameters, and the radiation flux can be claimed by the manufacturing The radiation flux can be claimed by the manufacturer, but the measured value should be no less than 90 % of the nominal value.
Table 6 UV radiation efficiency
| Nominal power range / W | UV radiation efficiency of double-ended lamps | UV radiation efficiency of single-ended lamps | UV radiation efficiency of self-ballasted lamps | Column 5 | Column 6 | Column 7 | Column 8 |
|---|---|---|---|---|---|---|---|
| <9 | 12 % | 12 % | 10.2 % | Column 5 Value | Column 6 Value | Column 7 Value | Column 8 Value |
*Ultraviolet radiation dose Q
UV radiation dose Q is the product of the radiation illuminance of the UV lamp used at the surface of the irradiated article and the irradiation time, calculated as follows.
Q = E × T
Where: Q – UV radiation dose, µW-s / cm²; E – UV lamp radiation illumination on the surface of the article, µW / cm² E T – the irradiation time of the UV lamp, s.
*Calculation of UV disinfection lamp power and disinfection time
Since different microorganisms are sensitive to UV light, the UV disinfection must be done in such a way that the irradiation dose reaches the dose required to kill the target microorganism. For example, 10 000 µW-s/cm² for general bacterial propagules; 100 000 µW-s/cm² for bacterial spores; between bacterial propagules and spores for germs; 600 000 µW-s/cm² for fungal spores, which are more resistant; and When the target microorganism is not known, the dose should not be less than 100 000 µW-s/cm². The dose should not be less than 100 000 µW-s/cm2.
From the above, the target microorganism can be determined by determining the dose of UV The irradiation dose Q can be determined by determining the target microorganism and the irradiation time T.
The irradiance is calculated as E = Q / T.
Based on the calculated radiation irradiance E, the area of the object to be irradiated A and UV radiation efficiency η (Table 6) can be selected as the appropriate UV The power of the UV disinfection lamp P = E × A / η = Q × A / (T × η). Similarly, according to the UV radiation dose Q and the power of the UV disinfection lamp P, the required irradiation time can also be found: T = Q × A / (P × η).
B. Indoor Air Disinfection
Indoor air disinfection using UV light is a method of direct or indirect irradiation of indoor air using UV lamps to achieve disinfection.
a. Indirect irradiation method: This is a method of indoor air disinfection using UV air disinfectors, which do not produce direct UV radiation to the indoor space and can be used in an occupied environment. High-intensity UV air disinfectors are generally preferred and have a reliable disinfection effect.
b. Direct irradiation method: Under unoccupied indoor conditions, a suspended or mobile UV lamp is used for direct irradiation of the indoor space. If you use a suspended UV lamp, you can usually use vertical downward irradiation, reverse irradiation, lateral irradiation, and other 3 kinds of irradiation direction.
Vertical downward irradiation, reverse irradiation means that the lamp is suspended under the ceiling, 1. 8 ~ 2. 2 m from the ground, direct vertical downward irradiation or reverse irradiation through the reflector; lateral irradiation means that the UV disinfection lamp is installed on the sidewall, and the lamp irradiates the side. Or install it on the wall of the aisle and irradiate downward to form screen-type irradiation.
According to the Disinfection Technical Specification (3rd edition), the number of indoor suspended UV lamps installed (30 W UV lamps with intensity greater than 70 µW/cm² at 1.0 m) is not less than 1.5 W per cubic meter on average. 1.5 W.
P total ≥ 1. 5 × L × W × H
N ≥ P total / P
where: P total – the power of the UV disinfection lamp required in the room, W.
L – length of the room, m.
W — width of the room, m.
H — room height, m.
N — number of UV disinfection lamps installed.
P — power of each UV disinfection lamp, W.
The engineering design is generally in accordance with the actual size of the indoor space, combined with the selection of UV lamps, the number of lamps required for scientific and reasonable design.
In actual use, because the radiation intensity of the UV killing lamp is inversely proportional to the radiation distance, so the installation is too high will affect the sterilization effect. Comprehensive consideration of the human respiratory belt in the effective irradiation range, the height of the hanging lamps is mostly 1. 8 ~ 2. 2 m. The layout of the lamps mostly adopts a uniform distribution type, in order to make space radiation intensity distribution uniform.
In addition, the use of UV disinfection lamps should also be regularly cleaned, so as not to use the dust accumulated on the surface of the lamp for a long time to impact its disinfection effect.
4) UV disinfection lamp distribution and control
The load level of UV disinfection lamps in the same place is usually the same as the load level of general lighting in that place. Therefore, the engineering design will generally design the fixed UV disinfection lamp together with the distribution system of general lighting, and for mobile UV disinfection lamps and UV disinfectors typically reserve sockets according to the power.
Since UV light has a certain effect on human skin and eyes, in order to prevent misuse, the control of UV disinfection lamps and general lighting should be set up strictly separately during engineering design.
According to JGJ 312 – 2013 Electrical Design Code for Medical Buildings, Article 8.5.2: The switch of the UV disinfection lamp should be different from the general lighting switch, and the installation height should be 1.8 m from the ground at the bottom. ② Timer switch control, set the time of UV disinfection irradiation according to needs, when the set time is over, the switch automatically disconnects; ③ Intelligent switch centralized control set the switch in the nurse’s desk or duty room and other places where there are medical personnel on duty centralized control and management.
In addition to the above specification requirements, the design should also be combined with the actual work requirements of specific hospital departments to UV disinfection lamps for comprehensive consideration to ensure reasonable design, effective disinfection, and safe use.
4 Summary
In the event of the COVID-19 epidemic, hospitals, as important places for saving lives and preventing epidemics, are very important for the health and safety of health care workers and patients.
Currently in the design of hospital UV disinfection, taking into account the low cost of fixed UV lamps, easy to operate in the consultation room, treatment rooms, blood banks, garbage disposal stations, mortuaries, and other places are widely used. However, there are certain limitations of fixed UV lamps, which should be fully considered and flexibly selected when designing. For example, UV lamps are usually installed in the center, with a height of 1. 8 ~ 2. 2 m, which may have a certain impact on the aesthetics, and other methods can be considered for places with strict aesthetic requirements; UV light will have a certain impact on human skin and eyes, and in order to prevent misuse, for places where non-professional personnel stay for a long time, such as wards, measures to prevent misuse should be fully considered or mobile UV lamp; for emergency situations, in the case of people must be dynamic disinfection of places can be used UV disinfector, such as infectious disease consultation room, treatment room, etc.
This paper introduces the disinfection of surfaces and indoor air by UV light, and discusses the design and application of UV lamps in hospitals, hoping to provide some reference for industry colleagues in specific project practice.
References
[1] GB 28235-2020. Hygienic requirements for ultraviolet disinfectors [S]. 2020
[2] GB 50849-2014. Building Design Code for Infectious Disease Hospitals [S]. 2014
[3] GB 19258-2012. Ultraviolet germicidal lamps [S]. 2012
[4]WS/T 367-2012. Technical specifications for disinfection in medical institutions [S]. 2012
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