The use of screens or barriers is fundamental to open beam Class 3B and Class 4 laser work. Many laser users wrongly believe that commercial, CE-marked laser windows and screens must be used. However, in contrast to laser safety eyewear, this is not the case.

The laser user may, for example, fabricate his own screen from some fire resistant material that is opaque at the laser wavelength. Other factors that should be considered for 'home made' free-standing screens include:

1. painting the inside surface of the screen a light matt colour to scatter incident light and provide maximum visual warning of a laser burn;
2. extending the screen from the floor to at least 2.5 m (a roof may also be needed);
3. completely surrounding the area, without gaps, and providing a labyrinth entrance.

A new standard EN12254 'Screens for laser working places - safety requirements and testing' came into effect during 1999, but compliance is not a requirement. The scope of the standard is limited to laser use up to a mean power of 100 W. Compliance should give the user confidence in the materials used and the method of construction, though further testing may be required.

Users should be aware that screens complying with EN12254 may yet be inadequate for their needs. This could occur if the actual beam area exceeds the minimum test area of 1 mm2 required by EN12254, or if the 100s test for 'stability to laser radiation' specified in the standard is inappropriate, for example if the screen is to be left unattended.

Pro Laser gives independent advice on the selection of commercial safety equipment.