Ordinary glass can cut off some UV that has a wavelength less than 300 nm.
An appropriate UV light source would be within the UV-A band because it’s the least hazardous UV radiation to work with. A risk assessment should be made on the type of UV light source used. Refer to local regulations or the school advisory service (e.g. SSERC, CLEAPSS) for guidance.
Use a screen around a UV lamp so that pupils are not exposed to its direct rays.
Even with UV-A care should be taken to reduce exposure to the source to as little time as possible.
We made use of a small, hand-held battery powered ultraviolet light source, which emits mainly UV-A radiation. These are supplied commercially as security devices to identify markings made with a UV marker e.g. such as the 6V mini UV Fluorescent lantern with torch. The one we purchased was supplied without a risk assessment - check local regulations or the school advisory service (e.g. SSERC, CLEAPSS) for guidance.
The output from an ultraviolet lamp is normally made visible by emitting some violet light – true ultraviolet is invisible.
Fluorescent lamps produce UV light by the emission of low-pressure mercury gas. Fluorescence occurs when UV is absorbed by a phosphorescent coating on the inside of the tube and re-emitted as visible light.
The sun is a source of UV. UV in sunlight can, in some cases, penetrate clouds, mist and fog. Fresh snow can reflect up to 85% of the sun’s rays.
Halogen bulbs or lamps that are not UV protected by a plastic or glass shield are another source of UV.
