UV TerminologyFig. 1 The Ultraviolet Spectrum
UV Radiation from Oriel® Lamp Sources
Our deuterium and arc lamp sources, spectral calibration lamps, Solar Simulators and Flood Exposure Sources produce UV with wavelengths down to 180 nm and below, depending on the lamp and the envelope material of the lamp (the optics on the lamp housing may block the shorter UV wavelengths). Our Quartz Tungsten Halogen Sources emit some radiation down to 220 nm. The UV intensity levels from some of these sources may be higher than those from the sun, and shorter wavelengths may be present. Carefully read this discussion as well as the Safety Instructions that are included with every UV source we ship, before operating the source.
Exposure to UV radiation, even for short periods of time, can be hazardous. The damage depends upon the exposure time, the intensity of the radiation, the wavelength, and the individual's sensitivity to UV. Since we cannot sense (see) UV radiation, we are not protected by any aversion or blink response.
UVB and UVC cause sunburn (erythema) and pigmentation (tanning). Long-term exposure results in loss of skin elasticity (premature aging). There is a well established connection between wavelengths below 320 nm and skin cancer (basal cell and squamous cell carcinoma) and growing concern over possible longer wavelength involvement. Action spectra for carcinogenesis peak at ~ 290 nm.
Corneal absorption of UVB and UVC may cause conjunctivitis and a corneal inflammation called photo keratitis. Initial symptoms of photo keratitis are: slight discomfort, which, after prolonged exposure, can develop into a temporary yet severe discomfort, an inability to look at bright light, and the loss of clear vision. Conjunctivitis (welder's eye) produces an uncomfortable sensation, similar to sand in the eye. Our innocuous pencil style mercury calibration lamps can cause this problem.Fig. 2 Threshold Limit Values for occupational exposure to ultraviolet radiation in an 8 hour period. These values for exposure of the eye or the skin apply to UV radiation from arcs, gas and vapor discharges, fluorescent and incandescent sources, and solar radiation, but they do not apply to UV lasers. (ACGIH ISBN: 0-9367-12-99-6)
Prolonged exposure to longer ultraviolet radiation, particularly UVA, may cause cataracts to form in the eye lens. Longer wave UVA may also penetrate to the retina and result in blue blindness.
UV Safety Precautions
The simplest thing to do if you don't need the ultraviolet is to get rid of it at the source. Use a lens or filter to accomplish this. If you require the UV then there are several precautions you should take to minimize exposure and reduce the hazards.
- Limit access to areas where UV sources are used
- Post warning signs at the entrance to labs or other work areas using UV sources
- Wear protective eyewear and gloves
- Cover arms and neck and limit exposure time
- Never look directly at the beam
- Use a manual or electronic shutter to close the beam when the source is not in use
- Use enclosed beam paths where possible
The U.S. National Institute for Occupational Safety and Health (NIOSH) recommends that exposure to UV energy be controlled and limited in the work place. Recommended maximum exposures are available, but these do not apply to photosensitive individuals or those exposed to photosensitizers.
The total intensity from 320 to 400 nm hitting an unprotected eye should not exceed 10 W m-2 for periods longer than 1000 seconds. For shorter exposure times, the energy density should not exceed 104 J m-2.