Guidelines, norms and standards in UV

Anyone who deals with norms and standards in the ultraviolet spectral range (UV) usually does so because of product safety or legal limit values in the workplace. So let us shed some light on this seemingly invisible world.

For products, it is necessary to differentiate between the intended applications in order to select the appropriate safety standard. Safety standards cover a wide range of product classes and applications. These can be roughly divided into different categories.

A distinction is made between electrical and electronic devices, machines, workstations and lamps/lamp systems.

Electrical and electronic devices are designed as household appliances, for example. For household appliances, it is assumed that they are also used at the workplace in an office-like environment. They therefore differ from appliances for industrial use.

The first relevant standard is therefore:

DIN EN 60335-1 VDE 0700-1:2024-07 Safety of electrical appliances for household and similar use

DIN EN or IEC 60335 consists of several parts, with the first part (60335-1) defining the general requirements. The specific requirements for different types of appliances are dealt with in separate standards (Part 2), such as

IEC 60335-2-27: Equipment for skin exposure to ultraviolet and infrared radiation

IEC 60335-2-65: Air purification devices (with UVC radiation)

IEC 60335-2-109:2010+A1:2013+A2:2016 Equipment for water treatment with UV radiation for household and similar purposes

IEC 60335 is regularly updated to take account of new technologies and changing safety requirements. The latest edition defines the free class of DIN EN 62471:2009 for UV safety, which we will come to later.

Notes: Older editions of IEC 60335-1 require in Chapter 32 (Radiation, toxicity and similar hazards): "Appliances shall not emit harmful radiation or hazards from toxic substances or the like during operation in normal use". The disadvantage of the old regulation is that no precise specification was included. Therefore, the free class according to DIN EN 62471:2009 is more advantageous, clearer and more precise.

As with EMC, for example, separate standards apply to machines and systems.

The most important is

DIN EN 12198-1:2008-11 Safety of machinery - Assessment and reduction of risks arising from radiation emitted by machinery

DIN EN 12198-1:2008-11 applies to machinery and lays down general principles for the assessment and reduction of radiation hazards that may arise from the use of such machinery. This includes various types of radiation, including optical radiation (ultraviolet, visible and infrared), electromagnetic radiation and ionizing radiation. DIN EN 12198-1 is applied if no applicable type C standard is available. The objectives and requirements of DIN EN 12198-1 are the assessment, reduction and identification of hazards.

The assessment distance to the machine is generally 10 cm. The classification is based on the effective irradiance and is divided into three classes:

The necessary protective measures and information then follow from the classification. It is not necessary to reduce the UV hazard to "zero" at this point. Conversely, however, the user must be warned and trained.

Note: For visible radiation in the range from 400 nm to 700 nm, the effective radiance or irradiance (Slamda) is used. This is not taken into account in the presentation of UV standards here.

This brings us to occupational safety in the workplace. Occupational safety with regard to UV radiation in the workplace is governed by guidelines and legal regulations aimed at protecting the health of employees and minimizing exposure to UV radiation. The main aspects that are taken into account are the OStrV (as for example in Germany) and Directive 2006/25/EC.

Ordinance on the Protection of Employees from Hazards Caused by Artificial Optical Radiation (OStrV)

This ordinance regulates the protection of employees from the hazards of artificial optical radiation, including UV radiation. It obliges employers to carry out a risk assessment and implement suitable protective measures. The OStrV exposure limit of 30 J/m² is part of the German Occupational Health and Safety Ordinance on the Protection of Employees against Risks from Artificial Optical Radiation, which transposes Directive 2006/25/EC into national law.

Directive 2006/25/EC Artificial optical radiation

Directive 2006/25/EC, known as the "Artificial Optical Radiation Directive", is an EU directive that regulates the protection of workers from hazards caused by artificial optical radiation in the workplace. The directive applies to all workplaces where workers may be exposed to artificial optical radiation. Artificial optical radiation includes ultraviolet radiation (UV), visible light and infrared radiation (IR) emitted by artificial sources such as lamps, lasers, welding equipment and other industrial applications.

Employers are obliged to implement the requirements of the directive in order to ensure the safety and health of their employees. This includes carrying out risk assessments, implementing suitable protective measures and providing regular training for employees.

The Artificial Optical Radiation Directive lists around 15 different hazards. The UV-relevant ones here are the limit values for incoherent UVA radiation HUVA and the effective irradiation of the skin and the eye Heff.  Further limits are included e.g. for the so-called Blue Light Hazard.

The effective irradiation of the skin and the eye Heff is explained here. This is a weighted irradiance. The weighting function is shown below. The diagram shows two curves representing the relationship between the wavelength (lambda) in nanometers (nm) on the x-axis and the hazard-response function S on the y-axis. The y-axis uses a logarithmic scale.

A high value of the weighting function means a high hazard. It can therefore be seen that the risk in the UVA spectral range is significantly lower than the risk from UV-B and UV-C radiation. 

The emission must be measured for the assessment. This is then multiplied by the weighting function S and multiplied by the exposure duration (in s). The result is the weighted dose H_eff. The limit value for H_eff is 30 J/m². The value is based on the minimum erythema dose (MED), which is the lowest dose of UV radiation that has been shown to cause erythema. The limits vary depending on the wavelength of the UV radiation, with shorter wavelengths (UVC and UVB) generally posing a higher risk than longer wavelengths (UVA). These limits are specifically defined for UV radiation with wavelengths between 180 and 400 nm. They represent conditions under which most healthy workers can be repeatedly exposed without suffering acute health damage such as erythema (reddening of the skin) or photokeratitis (a type of eye damage). These limits apply particularly to continuous radiation sources and are designed to provide a guideline that makes the use of UV sources safer, but should not be seen as a strict dividing line between safe and unsafe.

In conclusion, it can be said that the limit value of H_eff = 30 J/m² is applicable and has also been adopted in other standards. For example, it is adopted in the following ISO 15858:2016. Notes: Standards cannot specify legal limit values.

ISO 15858:2016 UV-C equipment ... Permissible exposure of persons

This international standard specifies safety guidelines for the use of UV-C radiation for the disinfection of air and surfaces. It is generally used for so-called upper-air UV devices for the disinfection of the upper airspace. ISO 15858:2016 defines the minimum requirements for the protection of people through an irradiance limit value that leads to a daily dose of effectively 30 J/m² at 254 nm emission. The UV-C irradiance is measured n between 1.83 m and 2.13 m [6.0 ft to 7.0 ft]) at various locations in a room. The measurements are carried out during initial installation and also when new UV lamps are installed.

The measurement differs from the general measurement procedure described in DIN EN 14255. DIN EN 14255 is generally applied.

DIN EN 14255-1:2005 Measurement and assessment of personal exposure to incoherent optical radiation

DIN 14255-1 specifies methods for the measurement and assessment of personal exposure to ultraviolet radiation from artificial optical radiation, including UV radiation. DIN EN 14255-1:2005 does not specify any limit values itself, but adopts these from the 2006/25/EC.  

In contrast to other standards, the assessment distance is not fixed, but is determined on an application-specific basis at the workplace. DIN EN 14255-1:2005 also specifies a series of protective measures and organizational measures, including personal protective equipment (PPE).

Finally, one or even the most important standard: the photobiological safety of lamps and lamp systems.

DIN EN 62471:2009-03 Photobiological safety of lamps and lamp systems

(IEC 62471:2006)

DIN EN 62471 was developed to ensure that artificial lamps and lamp systems do not have any harmful effects on the skin or eyes due to the emitted radiation. The wavelength range was defined as 200 nm to 3000 nm, which includes all hazards. DIN EN 62471 adopts the limit values of the Artificial Optical Radiation Directive 2006/25/EC and specifies measurement conditions, measuring instruments and evaluation distances. The evaluation distance is generally 20 cm.

The most important result is the evaluation and categorization into classes according to DIN 62471:

According to DIN EN 62471:2009, devices are to be classified into the following groups:

• Free group
• Risk group 1 (low risk)
• Risk group 2 (medium risk)

• Risk group 3 (high risk)

   

Devices in the free group do not show any:

• Actinic ultraviolet hazard (E_s) within 8 h
• Near UV hazard (E_UVA) within 1000 s
• Photochemical retinal hazard (L_B) within 10,000 s
• Thermal retinal hazard (L_R) within 10 s
• Infrared radiation hazard to the eye (E_IR) within 1000 s

Risk group 1 includes lamps that do not pose a hazard due to normal restrictions imposed by the user's behavior. This means, for example

• Actinic ultraviolet hazard (E_s) within 10,000s
• Near UV hazard (E_UVA) within 300 s

In risk group 2, the focus is on averting reactions to bright light sources or thermal discomfort. Risk group 3 (high risk) indicates that the lamp poses a hazard even for short-term exposure. 

A slight simplification of the assessment is possible according to the IEC 62471-6:2022 standard.

IEC 62471-6:2022 Photobiological safety of lamps and lamp systems - Part 6: Ultraviolet lamp products

Part 6 of 62471 also applies to lamps primarily intended to emit ultraviolet radiant energy, such as ultraviolet sources for excitation of fluorescence of irradiated materials, for insect light traps, for scientific studies, for mineral identification, for non-destructive testing, for germicidal irradiation and for other purposes. Therefore, radiance and thermal hazards are excluded. The evaluation distance of IEC 62471-6:2022 is application-specific and lies between 0.4 m and 3 m. For the application of Part 6 of IEC 62471, the UV radiation emission must be greater than 50% of the total radiation emission.

The IEC 62471-6:2022 standard deals with the photobiological safety of optical radiation sources, focusing in particular on photobiological safety requirements for optical radiation sources in LED-based systems. This supplement to the general standard IEC 62471 provides specific guidelines and requirements for the assessment and classification of UV LEDs and UV LED systems with regard to their photobiological risks.

Summary of GUIDELINES, NORMS AND STANDARDS IN UV

For the evaluation of a product, a machine or a workplace, the correct standard must be selected so that the measurement and evaluation conditions are specified. The most important ones have been listed.

In summary, the exposure limit value according to RL/2006/25 (Artificial Optical Radiation Directive) is of the greatest importance for UV assessment. This is 30 J/m² for a period of 8 hours. According to ICNIRP, the exposure limit of 30 J/m² applies to the exposure of the working population, but with some precautionary measures also to the general population. If the exposure limit is observed, it can be expected that healthy adults can be exposed repeatedly without acute adverse effects. According to ICNIRP, this limit should be regarded as a desirable target for skin exposure in order to minimize the long-term risk. ICNIRP points out that the exposure limit may also apply to the general population - but only with caution, as there may be sensitive individuals who could react negatively to exposure at these levels.

Outlook & Clarification for Far-UV at 222 nm:

The American Conference of Governmental Industrial Hygienists (ACGIH) published new exposure limits for 222 nm radiation in January 2022, increasing the levels for eyes and skin. The change is based on new scientific findings and research, but is not a legal limit. The national and EU limit value is an effective dose of 30 J/m² (2006/25/EC)!

The main reasons for increasing the exposure limits (at 222 nm) include:

Radiation at 222 nm, which is in the so-called far UV-C range, has a lower penetration depth into biological tissue compared to longer UV-C radiation at 254 nm. This lower penetration depth means that the radiation mainly reaches the outermost cell layers of the skin and the superficial layers of the eye without damaging the deeper, more sensitive layers.

For the eyes, the 222 nm radiation is also mainly absorbed by the outer layer of the cornea without reaching the deeper structures such as the lens.

Long-term studies have not yet been completed. Use is permitted up to the EU legal limit (30 J/m²) with the Seff weighting, but the ACGIH recommendation is not taken into account in the EU.