UVC safety at disinfection systems
UVC radiation can inactivate microorganisms, but uncontrolled exposure makes it a hazard to eyes and skin at the same time. A safety assessment of a disinfection system must therefore consider source, wavelength, accessible radiation, exposure time, distance and operating state together. Engineering shielding and interlocks take precedence over organisational and personal protective measures.
The inactivation mechanism itself is covered under UV disinfection; this page is about the hazard and how it is controlled.
System types by exposure risk
| System type | Typical exposure risk | Priority measure |
|---|---|---|
| Closed reactor or duct | Escape during maintenance or through leakage | Enclosure, interlock, maintenance release |
| Shielded surface system | Scattered and residual radiation | Enclosure, shutdown, measurement at the access points |
| Open room or air system | Direct or reflected exposure | Zone planning, access control, exposure assessment |
| Hand-held device | Proximity, misuse, changing angle | Design limits, clear operating rules, protective equipment |
| Far-UVC system | Exposure dependent on spectrum and time | Measure the full spectrum and check against the applicable limit |
Limit values, action-weighted assessment and risk assessment in detail are covered under occupational safety and photobiological safety.
Finally, a note on the so-called Far UV disinfection with 222 nm:
UV irradiation of skin for disinfection is generally not recommended. The Federal Office for Radiation Protection in Germany (BfS) advises against exposing oneself to intense UV radiation for disinfection. Caution is required when using UVC radiation. There is a risk of damage to the eyes and skin. The BfS also advises caution with devices that work with "Far-UV-C" sources. Of course, the requirements of occupational safety must be observed for these "Far-UV-C" wavelengths as well.
The following literature is intended to help in dealing with the issues surrounding UV disinfection:
CIE 155 "Air disinfection by ultraviolet radiation", 2003
CIE Position Statement on the Use of Ultraviolet (UV) Radiation to Manage the Risk of COVID-19 Transmission, May 2020
DIN EN 62471:2009-03 Photobiological safety of lamps and lamp systems; for UV lamp products additionally IEC 62471-6:2022 – Part 6: Ultraviolet lamp products
EN 14255-1:2005 Measurement and assessment of personal exposures to incoherent optical radiation - Part 1: Ultraviolet radiation emitted by artificial sources in the workplace
EN 14255-4:2006 – Measurement and assessment of personal exposures to incoherent optical radiation - Part 4: Terminology and quantities used in UV-, visible and IR-exposure measurements
ISO 15858:2016 UV-C Devices – Safety information – Permissible human exposure
ISO 15714:2019 Method of evaluating the UV dose to airborne microorganisms transiting in-duct ultraviolet germicidal irradiation devices
DIN EN 60335-2-65:2023-08; VDE 0700-65:2023-08 Household and similar electrical appliances – Safety – Part 2-65: Particular requirements for air cleaning appliances (supersedes the 2013-02 edition and its amendment A2:2014-04)
DIN EN IEC 60598-1:2022-03: Luminaires - Part 1: General requirements and tests (the EN 60598 series may be used as the basis for risk assessment considering mechanical, electrical and thermal safety)
Directive 2006/25/EC (Artificial optical radiation)
Regulation (EU) 2023/988 on general product safety (replaces Directive 2001/95/EC. The new regulation has been in effect since December 13, 2024.) In Germany, the Product Safety Act (ProdSG) supplements the regulation.
ICNIRP Guidelines on Limits of Exposure to Ultraviolet Radiation of Wavelength between 180 nm and 400 nm (Incoherent Optical Radiation) published in Health Physics 87(2): 171-186, 2004
GLA "Position Statement on Germicidal UV-C Irradiation UV-C SAFETY GUIDELINES" as of 05-2020
GLA "Germicidal UV-C Irradiation -SOURCES, PRODUCTS AND APPLICATIONS" as of 09-2020
Literature as of 12-2020
Note:
These lists of limit values, protective measures and requirements are not complete. The laws, guidelines and standards apply, in the respectively valid version with the respectively valid parts. All information is provided without guarantee and without claim to completeness.
How the effect itself comes about – fluence, dose-response curves and reactor technologies – is covered on the application page UV disinfection; the application to packaging materials and filling lines is described under packaging and filling technology.
Frequently asked questions on the duration of UVC disinfection
How long does disinfection take?
The time follows from the required fluence divided by the irradiance at the location of the organism. At 254 nm, four log reductions require about 8 mJ/cm² for E. coli, 22 mJ/cm² for Cryptosporidium and Giardia, 81 mJ/cm² for Bacillus subtilis spores and 167 mJ/cm² for adenoviruses; DIN 19294 and ÖNORM M 5873 set 40 mJ/cm² as the reduction-equivalent fluence. In a closed irradiation chamber shielded on all sides and delivering 10 mW/cm² this means seconds – the 40 mJ/cm² after four seconds. In an open room or air system that has to stay within the limit values for accessible radiation, the permissible irradiances are orders of magnitude lower; there the same fluence takes minutes to hours. A short exposure time therefore never implies that a system is safe: the safety assessment and the proof of efficacy are two separate exercises. The fluences per log level and the process limits are given under UV disinfection, the limit values under occupational safety and photobiological safety.
Author: Dr. Mark Paravia
Dr.-Ing. Mark Paravia is the managing director of Opsytec Dr. Gröbel GmbH in Ettlingen and heads the accredited calibration laboratory. Following his research on pulsed xenon excimer discharges at the Institute of Lighting Technology at KIT, his current focus is on optical radiation measurement technology. He is vice-chair of the DIN Standards Committee FNL 7 “Optical Radiation,” and a member of the DVGW Project Group on UV Disinfection.
