During the last few years a wide range of hand-held laser processing devices are being introduced into industry.  The extent of laser processing is extraordinarily wide.  This ranges from with the acceptance of laser processing as a method of cleaning sculpture and architectural buildings to the cutting and welding of ship components in the luxury liner construction shipyards. The use of hand-held laser devices is not limited to large size projects, hand-held laser processing devices are also used in the die tool reclamation industry and the manufacturer and repair of jewellery.  Currently there are no standard or guidelines to aid manufacturers and users in these applications, which are often in industries where laser processing is a new introduction.

To rectify this situation and give guidelines indicating best practice, the International Committees, responsible for laser safety (IEC/TC76) and optical equipment (ISO/TC172) are working together to extend the current standard for Laser Processing Machines (ISO 11553-1) with an accompanying standard for Hand-held Laser Processing Devices.  This will be published during the coming year as ISO 11553-2.

The purpose of the standard is to draw attention to the particular hazards related to the manufacture and use of hand-held laser and hand-operated laser processing devices and to prevent personal injury. This includes both the areas of hazard analysis and risk assessment as well as protective measures. The standard does not apply to medical applications, or processing machinery that deals with photolithography, stereo lithography, holography or data storage.

The principles outlined in standard (EN) ISO 12100 are used to identify the potential hazards generated by the laser processing device. The potential hazards include electrical hazards, thermal hazards, vibration hazards and radiation hazards, examples of which include hazards generated by the laser beam, hazards generated by ionised radiation, hazards generated by collateral (UV microwave etc) radiation and hazards generated by secondary radiation re-emitted by targets due to beam effects etc. In addition, hazards may be generated by materials and substances such as those hazards due to the products used in the laser-processing device itself (for example: laser gases, laser dyes, solvents), hazards resulting from the interaction between the beam and the materials being processed (for example: fumes, particles, vapours, debris), hazards from associated gases used to assist laser target interactions and from any fumes that are produced and hazards due to the leakage of liquids.  Significant hazards may also be introduced by neglecting ergonomic principles in the design of the hand-held laser processing device. Recognition also requires to be taken of the effects of power disruption or interference and the risks when human intervention into the hazard zone is necessary.

The environment in which many hand-held laser processing devices may be operated may be very diverse and thus the potential hazards due to the foreseeable environments need to be considered.  These environmental interferences include temperature, humidity, external shock/vibration, vapours, dust or gases from the environment, electromagnetic interference, lightning strike, source voltage interruption/fluctuation, insufficient hardware/software compatibility and integrity, non-observance of interface specification (including power limits, control signals).

There are many hazards that maybe particular to the use of hand-held laser processing devices. Many of these devices are used within confined spaces. In this case hazards to be considered are those due to the concentration of harmful substances in the room air, enrichment of the process gas in the confined space, oxygen depletion, increased radiation hazard through direct as well as directly or diffusely reflected laser radiation and increased tripping and impact (shock) hazard. Many devices are used in the construction industry and not a ground level.  Hazards to be considered here include falling objects, the potential user to fall.  The value of many held-held laser processing devices is that can be used outside the normal controlled industrial environment.  Thus hazards can be generated due to the prevailing environmental conditions, especially when the devices are being used outdoors.  Thus consideration requires to be made of ambient temperature (both cold and hot), humidity (rain, fog, hail), mechanical effects (vibration, wind pressure), electromagnetic effects (lightning strike), visibility (sunlight, lighting).

The proposed standard will introduce requirements to ameliorate these hazards. Generally the equipment shall comply with (EN) ISO 12100 and the principles contained in this generic standard. Manufacturers will be required to ensure the safety of hand-held laser processing devices by following the process of hazard identification and risk analysis, then implementing the appropriate safety measures, verifying those safety measures are effective and providing the user with appropriate information to allow the user to safely use the equipment. The manufacturer is responsible for compliance of the complete hand-held device with the requirements, including associated components (for example any handling unit, laser assembly). The measures applied are to eliminate or minimise all hazards identified as a result of hazard analysis and subsequent risk assessment.

Measures must be taken to provide protection against excess laser radiation. The possibility that people, such as onlookers, be exposed to levels of laser radiation exceeding the Maximum Permissible Exposure (MPE), as defined in standards IEC 60825-1 and -14, shall be eliminated during operation. Unauthorised human exposure above the MPE shall be prevented by engineering or administrative measures as stipulated in IEC 60825-1 and ISO 12100. One and the same protective device may be used to provide simultaneous protection against more than one hazard.

During operation, the principal danger zone is usually the process zone but the danger zone must be defined as a result of the risk assessment. The Nominal Ocular Hazard Area (NOHA) is defined in IEC TR 60825-14 as the volumetric space where laser radiation may exceed the MPE.
At the process zone, human exposure shall be limited during normal operation to levels of laser radiation not greater than the MPE for 3 x 104 s exposure duration (e.g. by local protection using a protective enclosure; or by the provision of personal protective equipment).

During service intervention, human access to laser radiation exceeding the Accessible Emission limit (AEL) for Class 1 is sometimes unavoidable. During servicing it shall be ensured that only authorised persons are allowed access to zones exposed to levels of laser radiation that exceed the AEL values for Class 1. Hand-held laser-processing devices shall therefore be designed and appropriate safety measures provided, with respect to the following four situations listed in order of preference:

• Servicing takes place outside danger zones.
• Servicing takes place in danger zones to which access is controlled in the same manner as during production (for example interlocked cover).
• Servicing takes place in a danger zone (for example with open guards that are normally closed during production) but accessible laser radiation does not exceed the AEL for Class1.
• Servicing takes place in danger zones, for example because opening of guards (normally closed during production) is necessary. In this case accessible laser radiation exceeds the AEL for Class 1.

The manufacturer shall indicate the class of accessible laser radiation and recommended safety procedures for each of these situations (as applicable). When servicing hand held laser-processing devices, the laser device should be switched off. For activities (e.g. adjustment), where this is not possible, a nominal ocular hazard area shall be established.

The standard ISO 11553-2 outlines the range of requirements for the design of hand-held laser processing devices. The requirements include design features for the protective housing, emission warning devices, control of scanning laser devices, Emergency stopping, general control means, interface and beam delivery means.  The standard also includes verification methods to ensure conformance to the requirements of the standard together with requirements for User information.

The standard concludes with examples of risk assessments.  A useful bibliography of associated standards is also included to aid designers.

It is intended that the standard ISO 11553-2 will be published during 2006.  There is clearly a need for this document as the number of hand-held devices increases and the potential applications become a reality. One aspect that is not included in the standard is that of noise.  Many applications generate high levels of noise either from the equipment or from the process itself.  Recent legislation in the form of amended Regulations mirroring the latest EU Directives, require the control of noise.  The requirements for this application are still being negotiated with the EU Consultants for Noise. However the Technical Committee dealing with this Standard believes that it is important not to delay the publication of the standard and thus an amendment to include the requirements for noise will be issued in 2007 or 2008.