Throughout history people have been exposed to high levels of infra-red radiation, in the making of steel or glass, simply being out in strong sunlight, in fact anywhere close to a hot object. Infra-red gives a heating effect, which we sometimes use to keep us warm, but too much on the skin can cause blistering. Industry is aware of the dangers of high intensity IR radiation and the risks and effects of over exposure to it are well known.

Bright natural light which contains infra-red causes the eye to blink, the iris to contract and the viewer to look away. These normal defence mechanisms do not happen when the visible part of the light has been removed. The eyes are more sensitive than the skin, over exposure for long periods may give rise to retinal damage and cataracts. These are the hazards of over exposure to IR. The exposure limits ^(1,2,3) and fig.1 show that filtered IR is around 100 times less hazardous than visible blue light.

Other sources of IR are lasers which give high intensity beams, these intense beams have necessitated safety regulations. These regulations encompass conventional light sources. Derwent have reviewed these regulations ^1,2,3, and have produced the following guidelines for the use of their products.

There are two scenarios which have to be considered with these security systems, safety in use which is long term and safety during installation, testing and maintenance which is shorter term. Details of the technical aspects which were used to arrive at these recommended minimum safe working distances are given later.