The circumstance of unenclosed Class 3B or Class 4 laser beams crossing a walkway occurs surprisingly frequently, in both the laboratory and the factory environment. Examples include beams crossing between optical tables or from an optical table to target chamber or, in the factory setting, from a high power laser to a large area cutting table, during servicing when access to the beam is required. Not surprisingly, beams crossing walkways are specifically highlighted in the EN60825-1 user guide as something to be avoided in beam path design, but occasionally there is no reasonable alternative. A high power laser feeding a flying-optic cutting table, for example, might be located away from the table in order to minimise the variations in beam diameter at the focussing head that occur as the head travels over the table. In addition, there is the problem that with the table at waist height and the optics mounted above the table, the beam path is often at head height.

In a factory environment, the beam might be enclosed in a secure, appropriately-labelled robust metal tube, protected from external impact and cushioned to prevent injury to personnel passing underneath. In service mode, however, if the laser is to be operated with the tube removed, then a barrier and warning signs may need to be erected. We are personally aware of two cases of facial CO2-laser burn injuries in as many years, both of which could have been avoided had such obvious precautions been taken. In the laboratory setting, beams crossing walkways will almost always be at waist, not head, height. Also, the laboratory staff will be trained in the use of laser safety eyewear. Nevertheless, a Class 4 laser beam poses a skin/fire hazard and additional measures need to be carefully considered. Tubes at waist height can be a serious obstacle hazard, but fortunately there are a number of satisfactory solutions that can be considered. These include (in general order of effectiveness) beam shutters linked to a light curtain or pressure pad at the beam crossing point, hinged tubes (with the raising of the tube simultaneously blocking the beam) and use of retractable tapes.

Pro Laser specialises in providing practical solutions to safety problems. We also offer safety audits, risk assessments and safety training appropriate to the users specific needs.