Opposing the 2016 Mercury Vapor Lamp Ban
U.S. Congress and NEMA
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What we are asking is for U.S. Congress to vote against this and for NEMA to drop the proposal. There are multiple reasons why we feel that mercury vapor lamps should stay around. One benefit of the mercury vapor lamp is that they have the longest life out of all of the HID lamp types. Although rated for 24,000 hours, some mercury vapor lamps that were installed in luminaires such as streetlights were removed from their respective fixtures 20, 30 and even 40 years later by linemen and the lamps still illuminated brightly when tested (5.) Lineman Steven Pedri of Baltimore Gas and Electric and avid streetlight enthusiast Joe Maurath Jr who has lived in a house with a utility owned 100 watt mercury vapor luminaire for over 20 years can testify to that. Pedri has also noticed that mercury vapor luminaires seem to be the most reliable and trouble free of the HID family.
Long life and reliability are good things, but they are not the only reason to keep mercury vapor fixtures in use. Mercury vapor lamps are beneficial towards trees. It has been well known that trees go through a dormancy cycle during the nighttime period of a single day. According to a study performed by William R. Chaney of Purdue University's Department of Forestry and Natural Resources (1,) the color spectra of different light sources have different effects on trees. Trees sense when there is light, and when they don't sense light, they can go through their regular dormancy cycle. Chaney's study found that trees that were exposed to continuous light sources that were high in red light sustained more injuries due to the lack of their dormancy cycle than those that were exposed to continuous light that was high in greens and blues, which is probably because plants absorb red light and reflect green light. Mercury vapor lamps come in two types, clear lamps and phosphor-coated lamps. The phosphor coating is to add red to the spectrum, which is low in the case of clear mercury vapor lamps. Clear mercury vapor lamps have a spectrum which peaks in a few colors, mostly greens and violets. This makes clear mercury vapor lamps optimal for areas with trees since the light that they produce would go unnoticed by the trees, thus allowing them to go through their standard dormancy cycle. In addition to being beneficial for the health of trees, a many landscapers prefer clear mercury vapor lamps (4) because the blue green hue is complimentary to the leaves and bark of the trees as well as other plants, making the green areas of the trees and other plants pop out a lot more.
Trees are not the only life forms that can benefit from mercury vapor lamps. Humans can benefit from the increased visibility. As discussed earlier, clear mercury vapor lamps produce a color that is high in greens and violets while the phosphor-coated lamps produce more of a fluorescent white color. The human eye is most sensitive to green light and least sensitive to red light. An article published by James Madison University on light levels (2) observed a finding discovered by the Illumination Engineering Society of North America comparing metal halide lamps with high pressure sodium in terms of usable lumens. The discovery found that it took 4 times as many high pressure sodium lumens to equal the same amount of visibility as a single metal halide lumen. This is probably because high pressure sodium lamps have a spectrum that is high in red and yellow light but low in blue or green light. This would mean that while high pressure sodium lamps are technically the most efficient HID light source in terms of cumulative lumens, they are not the most efficient when it comes to usable lumen. Like phosphor coated mercury vapor lamps, metal halide lamps also produce a fluorescent white color most of the time. I have also noticed a high visibility with clear mercury vapor lamps, which is likely caused by the strong presence of green light in the clear mercury vapor lamp spectrum. In addition to having the benefits of a higher visibility, the USDA observed a survey performed by a utility company (3) that found that their customers preferred mercury vapor lights over high pressure sodium ones by a 4 to 1 margin. According the USDA, this was mostly because the customers preferred the color of the light source.
Outdoors isn't the only place mercury vapor lights are used. I personally am a photographer and musician. I like to use clear mercury vapor lights for my photography because of their unique spectrum. This spectrum provides a higher contrast when used on people than other light sources. This is especially good for black and white photography. I also enjoy using a clear mercury vapor flood light to illuminate myself when I am performing as a musician because I have found nothing that can duplicate the unique spectrum. I also will use phosphor coated mercury vapor lamps as indoor lighting in my home sometimes because the color is very soothing and stable.
Stability is a big benefit with the mercury vapor lamp. Mercury vapor lamps don't burn out often. Over time, they get dimmer and dimmer. This is due to blackening inside the quartz arctube from the electrodes sputtering as the lamp is started. The Westinghouse corporation once made a mercury lamp called the Lifeguard, which had an extra chemical inside the arctube that slowed down the blackening process by making the arctube deposits from the sputtering turn white instead of black, allowing more light to go through. These lamps were invented in 1961 and made all the way until1985, and then made by Philips after the buyout until the early 90's. Sylvania had their version of the lamp called the Banner lamp and General Electric had their version called the Bonus Line lamp. These were the types of mercury lamps that were known for lasting well beyond their rated life (5.) When a mercury vapor lamp does finally stop working, it is usually because the arctube is completely blackened.
High pressure sodium and metal halide lamps both have their drawbacks as well. High pressure sodium lamps exhibit a phenomenon called "cycling" when they are getting close to burning out. Cycling is when the lamp turns itself off, and then it has to cool down before it can re-strike. Sometimes newer high pressure sodium lamps with a good amount of life left will cycle when there are fluctuations in the line voltage as well. In areas where high pressure sodium lights are plentiful, it isn't uncommon to see one or more of them cycling. Metal halide lamps have a white color similar to a phosphor coated mercury vapor lamp with twice the efficiency but are rated at half the life expectancy of mercury vapor lamps. Since the elements inside a metal halide arctube are a mixture or aggregate of different elements, usually not all metal halides will be the exact same color, something that can be seen in mercury vapor or high pressure sodium lights. In addition to having differences in hue, metal halide lamps are prone to exploding when they burn out. Since metal halide lamps contain mercury, just like mercury vapor and high pressure sodium lamps, this has the potential to release mercury into the atmosphere. This usually requires that metal halide lamps either have a protective shround around the arctube to keep the outer bulb from rupturing, or that they are used in luminaires that are totally enclosed. Because of their violent mode of failure and the instability of the arctube mixture, some metal halide lamps see well less than their rated life expectancy. Higher quality metal halide lamps such as Sylvania Metalarcs tend to see their rated life expectancy most of the time.
Because of these drawbacks, we feel that neither metal halide nor high pressure sodium lights are the ideal choice in some situations. We feel that for our purposes, mercury vapor lamps are usually a good choice because of their performance to cost ratio. They produce a nice high visibility white light like a metal halide or a high visibility blue green one, while maintaining a lower cost and color consistency of a high pressure sodium fixture without the drawbacks of either. Mercury vapor lamps never cycle and rarely explode. To us, this is the best of both worlds, plus other benefits. Mercury vapor lamps also last longer than either of the other two HID light sources. As far as efficiency goes, the mercury vapor lamps is still substantially more efficient than either incandescent or quartz halogen lights, which are still allowed because people prefer them for their aesthetic reasons. Mercury vapor lamps are also slightly more efficient than fluorescent lamps, which are becoming more and more popular as incandescent replacements these days for their efficiency. If we can keep those lamps around, why not mercury vapor as well? We believe that all the light sources have their uses someplace and that the market should be what decides. About 30\% of the street lights in the U.S. are mercury vapor and still working. In addition to that, many people who live in rural areas use mercury vapor lights to light their yards or the barns on their farms. We believe that it wouldn't be fair to those people to have to take down their working fixtures as a result, especially if they felt that a mercury vapor luminaire best suited their purposes. As a result, we would like say no to bulb bans.
For the aforementioned reasons, we, the undersigned, would like to urge NEMA not to ban the mercury vapor bulb and for U.S. Congress to vote against such a proposal should the opportunity occur.
1. Chaney, William R. (2002, June) Does Night Lighting Harm Trees? Retrieved from the Purdue University Department of Forestry and Natural Resources website: http://www.ces.purdue.edu/extmedia/FNR/FNR-FAQ-17.pdf
2. MacNutt, Alan D. (n.d.) Illumination Engineering Society of North America (IESNA) Light Levels. Retrieved from the James Madison University public safety website: http://www.jmu.edu/safetyplan/lighting/iasnalevels.shtml
3. Norman, Mike. (n.d.) Security Lights High Pressure Sodium or Mercury Vapor? Retrieved from the United States Department of Agriculture website: http://www.usda.gov/rus/electric/engineering/1999/securitylights.htm
4. Halper, Jeff. (2009, July 27.) Exterior Worlds Houston Tree Lighting. Retrieved from the Exterior Worlds Landscape Designers blog website: http://www.exteriorworlds.com/blog/2009/07/houston-tree-lighting.html
5. Maurath, Joe Jr. (n.d.) Mercur-Vapor Lighting. Retrieved from Joe Maurath Jr.'s vintage streetlighting history website: http://www.vintagestreetlights.com/history/mercury.html