UV Curing Safety

UV Chemistry

Like any industrial chemical, un-cured UV Materials should be treated with care. Refer to the MSDS (material safety data sheets) provided by the UV-material supplier for specific guidance on the actual UV material being used. Many UV materials can irritate the skin and mucous membranes (eyes and nose). Always wear latex gloves when handling UV material and wash any residue from the skin with soap and water. Material left on the skin for a period of time can cause an itching sensation and ultimately a rash. Keep hands away from eyes, nose, and mouth. Wash hands thoroughly before smoking, eating, or going to the bathroom. Once cured, the UV material can be handled normally without any concerns.

UV Light

Although UV light occurs naturally, especially on a sunny day, the intensity of UV light emitted by a UV lamp is much greater than found outdoors. UV lamp system manufacturers routinely incorporate shielding to protect the operator from this high intensity UV light. A properly designed light shield should prevent the operator, when in a normal position, from looking directly at the bulb or at the cure zone (where the focused light from the lamp strikes the substrate being cured). Secondary reflections contain a lower level of UV light (due to the poor UV reflectivity of most materials), but they still need to be controlled. As a general rule of thumb, light that is uncomfortable to the eye should not escape from the lightshield. A glow of light from a light shield is considered a safe level. In some cases, it is not feasible to reach this level of light attenuation. In those instances, proper protection of eyes and skin is necessary. This includes UV blocking glasses, gloves, long sleeve shirts, and possibly face protection. Never look directly at the bulb or cure zone.

UV light has well-known effects on unprotected skin and eyes. Sunburn is caused when the skin absorbs too much UV light. The unshielded light from a UV lamp can cause the same kind of burns. Snow blindness or "welder's eye" occurs when too much UV light is absorbed by the outer surface of the cornea. Direct light from a UV lamp can also cause this condition. UV burns to the skin and cornea, though normally painful, completely heal in a few days time.

Ozone

Ozone is a type of oxygen molecule, created when a normal 2 atom oxygen molecule is broken apart by high energy and then recombines into the 3 atom ozone molecule. In nature, UV light from the sun and the electrical discharge of a lightning bolt both create ozone.

Oxygen absorbs UV strongly in the 185nm wavelength. During lamp start up, the cold quartz tube transmits 185nm UV. As the quartz heats up to operating temperature, the transmission curve of the quartz shifts towards the longer wavelengths and 185nm light is no longer able to pass through the quartz. For this reason, ozone is generated by UV lamps mostly during start up.

In the concentrations found in UV curing systems, ozone can possibly irritate the mucous membranes of the eyes, nose, and throat. Most UV systems are designed to discharge exhaust air outside the plant to eliminate this possibility.

Ozone is very unstable, and rapidly decomposes to oxygen in the presence of UV light moisture, metals, organic materials and heat. Since these materials are prevalent in the UV curing process, ozone produced by the lamps quickly decomposes.

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