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[Note: NEA has issued an advisory on the use of ultraviolet-C (UVC) sterilisers in the home, where we do not recommend the use of UVC sterilisers that do not have safety features to prevent accidental exposure in homes. The advisory can be found here on the Use of UVC Sterilisers in the Home]
Background
Ultraviolet Germicidal Irradiation (UVGI) is a disinfection method that uses UVC. This method of disinfection has been applied in the disinfection of surfaces and sanitisation of drinking water. UVC sterilisers which use UVGI have been applied in the healthcare sector and in research. The efficacy of UVGI against a range of microbes has been demonstrated in numerous studies.
UV disinfection has a short turn-around time (less than 30 min) and does not leave any chemical residues behind after treatment. However, the following factors must be considered when it is applied, whether as a fixed installation or as a portable system:-
There must be line of sight from the UVC source to the surface to be disinfected for treatment to be effective. High-touch points that are obscured may be missed. For example, surfaces of door handles, handle bars, or toilet flushes that are not directly in the line-of-sight will not be disinfected.
The effectiveness of UVGI in inactivating microorganisms depends on the duration of exposure, intensity, distance of surface from source and wavelength of the UV radiation. There is therefore a need for careful calibration and monitoring.
Safety Guidelines
There has been a growing demand and enquiry for UVC disinfection devices, and an increased availability of such devices in the market.
In this regard, it is important for members of the public to be aware that these devices should be handled safely as UVC radiation can cause eye injury (for example, irritation and inflammation of cornea) and skin injury (for example, erythema). In addition, some of these UVC devices may also emit ozone, which can irritate the nose, throat and lungs.
For those who have respiratory sensitivity such as asthma or allergies, the use of such UVC devices that emit ozone should be avoided and checks should be done with the manufacturer to verify whether the device emits ozone. All UVC devices are to be kept out of reach of children.
UVC devices should only be operated by trained personnel to avoid accidental exposure to the personnel and others at the premises.
The safety guidelines listed below should be followed when using UVC disinfection devices.
Training 1. Personal training should include the following: a. Use of appropriate personal protective equipment (PPE) b. Health and safety topics – For example, the effects of UVC radiation on the eye and skin, the need for control of the hazards involved and the hazards associated with accidental UVC exposure in work areas. c. Safe handling of UVC device – For example, the safety precautions, maximum permissible exposure limits (if the device manual does not contain the information, it should be requested from the manufacturer), location of emergency stop button to power off the device or stop the UVC irradiation. d. First aid response post exposure
Limitation of access 1. Personnel working with the UVC disinfection device should ensure that there is no person in line of sight of the device when it is in operation, so that there are no risks of exposure. Some examples are listed below: a. If a UVC disinfection robot is to be used in an enclosed space, ensure that the space is vacated before commencing operation of the UVC robot. b. If a UVC disinfection robot is to be used in an open space, restrict access to the area and ensure that the UVC robot is a safe distance away from people. Safe distance is the distance from a source within which the irradiance for a given exposure duration does not exceed the exposure limits stated in the International Commission on Non-ionizing Radiation Protection (ICNIRP) guidelines on limits of exposure to UV radiation of wavelengths between 180nm and 400nm (incoherent optical radiation). Please check with the manufacturer on the safe distance for the specific UVC device. c. In the case of upper room UV germicidal irradiation (UVGI) lamps, the lamp fixtures must be carefully installed to minimise exposure of UVC to occupants in the room. The limits for exposure to UV incident radiation on unprotected skin or eyes apply to exposure within any 8-hour period. The exposure limit for effective radiant exposure is 30 J/m2. This limit is specified under the ICNIRP guidelines on limits of exposure to UV radiation of wavelengths between 180nm and 400nm (incoherent optical radiation) and the International Electrotechnical Commission (IEC) 62471:2006 Photobiological safety of lamps and lamp systems.
2. When any mobile UVC disinfection device is not in use, ensure that it is stored or kept in a manner so as to prevent unauthorised access.
Hazard Warnings 1. There should be warning labels on all UVC disinfection devices to indicate the presence of a UVC hazard. Warning labels should include the following: a. A UVC warning symbol (below is an example of a symbol in accordance with the IEC 61549-310-1)
b. A warning sign that eyes and the skin must be protected When warning labels are damaged or unreadable, they should be replaced immediately. 2. Warning labels should be used to indicate that the device is energised. 3. In the case of upper room UVGI lamps, warning signs should be placed near the lamps and on AHU access panels where the internal UVGI lamps are installed. Activation switches should be clearly labelled and protected with switch guards to prevent accidental activation by unauthorised persons.
Personal Protective Equipment 1. Anyone working on a UVC device should wear appropriate PPE when operating or servicing the device at all times. Examples of PPE include the following: a. UV-resistant eyewear (goggles/face shields/safety glasses) b. Protective wear/clothing, which covers exposed skin
Self-assessment Checklist A checklist on safe deployment of UVC disinfection devices (derived from the safety guidelines) can be downloaded below. We encourage premises owners or operators to fill in the checklist in order to self-assess that the deployment of the UVC disinfection device is safe.
Checklist on safe deployment of UVC disinfection devices/ checklist [DOCX, 150KB]
References
Branche, C.M. (2009) Environmental control for tuberculosis: Basic upper room ultraviolet germicidal irradiation guidelines for healthcare settings. U.S. Department of Health and Human Services, Centre for Disease Control and Prevention, National Institutie for Occupational Safety and Health, NIOSH Publication No. 2009-105.
Lindsley, W.G. et al (2018) Ambulance disinfection using Ultraviolet Germicidal Irradiation (UVGI): Effects of fixture location and surface reactivity. J. Occup. Environ. Hyg. 15, 1-12
[Source: National Environment Agency - Safety Guidelines for Use of UVC Devices in Commercial/Industrial Settings]