MERCURY VAPOR LAMPS

Mercury Vapor Lamps in a GymnasiumMercury vapor lamps are widely used to light both indoor and outdoor areas such as gymnasiums, factories, department stores, banks, highways, parks and sports fields. These lamps are potential emitters of ultraviolet radiation (UV). Mercury vapor lamps consist of an inner arc discharge tube constructed of quartz surrounded by an outer hard borasilicate glass envelope. Shortwave UV, a result of the decay of mercury atom electrons from an excited to a stable state, is readily transmitted through the inner quartz tube but is virtually blocked by the outer glass envelope during normal operation. Partial or total removal of the outer envelope allows the shortwave UV radiation to emanate from the lamp. In addition, the lamp may continue to operate for several weeks with the outer protective glass envelope broken. The resulting exposure to UV radiation from such a lamp causes erythema (skin burns) and photokeratitis (inflammation of the eye) which may lead to permanent eye damage. Extensive or repeated exposure may lead to premature aging of the skin or skin cancer in later years.

The Food and Drug Administration's Safety Performance Standard for mercury vapor lamps effective March 1980 (21 CFR 1040, Federal Register Volume 44, No. 175, p. 52191) permits the manufacture of two types of lamps. One type has a self-extinguishing device that will shut the lamp off within 15 minutes after the outer globe is broken. These lamps are marked "T". The following label will appear on the packaging of self-extinguishing mercury vapor lamps and metal halide lamps: "This lamp should self-extinguish within 15 minutes after the outer envelope is broken or punctured. If such damage occurs, TURN OFF AND REMOVE LAMP to avoid possible injury from hazardous shortwave ultraviolet radiation." It should be noted that a "self extinguishing" lamp may take as long as 15 minutes to turn off after the outer bulb has been broken. Therefore, if the lamp breaks, even if it is self-extinguishing, people should leave the area immediately.

The second type of mercury vapor lamp does not have a self-extinguishing device incorporated into the lamp. This type of lamp should only be used in a totally enclosed lighting fixture with a glass or plastic shield that will absorb the hazardous UV radiation, or in areas where people will not be exposed to UV radiation if the outer globe is broken. These lamps are marked "R". The following label must appear on the packaging and advertising for non self-extinguishing mercury vapor and metal halide lamps: "WARNING: This lamp can cause serious skin burns and eye inflammation from shortwave ultraviolet radiation if the outer envelope of the lamp is broken or punctured. Do not use where people will remain for more than a few minutes unless adequate shielding or other safety precautions are used. Lamps that will automatically extinguish when the outer envelope is broken or punctured are commercially available."

The use of mercury vapor lamps in New Jersey is regulated under N.J.A.C. 7:28-41, Mercury Vapor Lamps. Requirements for the indoor use of mercury vapor lamps can be found in N.J.A.C. 7:28-41.3(a). The requirements state that for indoor use, the mercury vapor lamp must be of the self-extinguishing type or if it is non-extinguishing, it must be installed within a totally enclosed lighting fixture with a protective shield which protects the lamp for damage and absorbs shortwave UV radiation. Requirements for the outdoor use of mercury vapor lamps can be found in N.J.A.C. 7:28-41.4(a). If people are likely to remain in an outdoor area of illumination for more than 15 minutes, the same provisions found in 41.3(a) must be met. However, 7:28-41.4(b) states that the Department may exempt certain outdoor installations from the provisions of 41.4(a) if it determines that sufficient precautions have been taken to minimize the possibility of overexposure to shortwave UV radiation.

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