By RICHARD MANDEL, senior editor

Since the use of lasers in welding applications continues to expand in independent and hybrid-combination systems, it's important to take a moment to consider that, as in MIG and TIG welding, not all the safety concerns are about hot metal. As in MIG and TIG, the plasma arc produced during laser welding produces high levels of UV light capable of delivering serious burns to exposed skin. In addition, laser light bouncing off of reflective surfaces poses secondary radiation hazards, particularly at the energy levels involved in an industrial process.

Welding laser systems that operate in an open beam configuration are designated as Class IV lasers. The Class IV tag refers to a system that may present an eye and skin hazard under most common exposure conditions, either directly or by reflection during operation or maintenance. According to safety protocols recommended by Michigan Technological University, three aspects in a laser application influence the total hazard evaluation:

  • The laser or laser system's ability to injure personnel.
  • The environment in which the laser is used.
  • And, the personnel who may use or be exposed to the beam.

All three aspects must be considered to establish control measures that are commensurate with the potential hazard.

According to the ANSI Z136.1 standard, a Class IV laser system should have a Nominal Hazard Zone designated for the equipment. The zone is the space around the laser equipment within which the level of direct, reflected, or scattered radiation during normal operation may reach or exceed a level of safe laser radiation exposure. The nominal zone is unique for each machine, and is based on the power or energy output; beam diameter; beam divergence; pulse repetition frequency; wavelength; beam path (including reflections); beam profile; and the maximum anticipated exposure duration.

Additionally, the standard recommends that the operator control the machine from a firing and monitoring location that is remote from the laser beam and its target.

Further along in the ANSI standard are descriptions of the engineering controls that are required for safe operations. Standard 6.3.2 recommends interlocks and warning devices on machines that use laser devices, while Standard 6.3.3, which is specific to Class IV equipment, addresses the use of a laser-processing machine that is not completely enclosed. "Operation shall occur only in a light-tight area with interlocked entrances, remote controls, and ‘panic button' for emergency deactivation of the system," the standard says.

Typically, most lasers that operate in an open beam system are enclosed in cabinets that have specially treated windows. The windows absorb most of the laser's secondary radiation, along with most of the plasma arc's UV radiation.

Where there is risk of secondary radiation leakage in a laser welding area, most welding clothing provides adequate protection to the workers. However, laser light is different from the light of a welding plasma arc, so it requires different protection for the eyes. Such eye protection is not specified for laser welding in either OSHA Standard 1926.102 or the Department of Energy's OSH Technical Reference — rather, eye protection for welding is specified separately from protection from laser light. There are currently no eyewear products that suitably provide combined protection from laser and welding radiation, but the good news is that laser safety glasses are available in styles that resemble eyeglasses and can be worn comfortably under a welding helmet.

Many shops take the extra measure of designating a laser safety officer who is responsible for personnel protection, laser cell class conformance, and enforcement of all laser safety regulations. That step helps to ensure smooth, safe transitions as more companies adopt laser-welding technologies.