the room are colored with a high-reflectance color. Lighting  is,  however,  only  one  of  many  factors  that make  up  the  whole  environment.  While  the  highest lighting efficiency may be maintained in a completely white   room,   the   psychological   effect   of   such surroundings  on  the  occupants  may  be  less  than harmonious. The use of color in the surroundings, even if it means sacrificing lighting efficiency, is necessary for  the  well-being  of  the  occupants.  Ceilings  should have the lightest color, preferably an off-white. Shiny surfaces should be avoided, as they result in glare. As mentioned  earlier,  lighting  levels  start  dropping immediately after the installation of the fixtures. Lamp burnouts and lamp depreciation contribute to this, but the principal cause is the accumulation of dirt. It is not uncommon to find lighting levels one half of the initial values after only a year or so of operation. The lighting maintenance  program  must  include  cleaning  and painting  of  the  walls  and  ceilings  in  addition  to  the fixture cleaning schedule. When  mounting  any  light  fixture,  follow  the manufacturers’ step-by-step instructions. The most important thing to remember when mounting any fixture or device is to ensure that all connections are both electrically and mechanically secure. High-intensity  discharge  lamps  (HID)  will  be discussed further in chapter 6. TROUBLESHOOTING  LAMPS As light sources are designed to operate most efficiently  and  economically  at  their  rated  voltages, special emphasis should be given to using lamps to suit the voltage of the circuit. Operation within the normal operating range is desirable; because both overvoltage and undervoltage operations have a determined effect on the life, efficiency, and economy of the light source. The effect on lamps operated over or under their rated voltage range is described below. FLUORESCENT  LAMPS Line voltage higher than the maximum of the ballast range will shorten lamp and ballast life. Line voltage   below   the   minimum   range   will   reduce illumination and may cause uncertain starting of some types of fluorescent lamps. INCANDESCENT  LAMPS Line voltage higher than the maximum lamp range will increase the light output but will shorten lamp life. Line  voltage  below  the  minimum  range  will  extend lamp life but will reduce light output approximately 3 percent for each 1 percent in voltage drop. MERCURY LAMPS Line voltage higher than the maximum lamp range will shorten lamp and ballast life. Line voltage below the minimum range will reduce illumination and may cause uncertain starting. LAMP GUIDES The  most  common  troubles  encountered  with  lamp equipment, the probable causes, and the suggested solutions are contained in table 5-6. MAINTENANCE OF LIGHTING SYSTEMS Lighting has a great influence on the quality and quantity of work as well as a direct bearing on employee morale. The necessity for periodic attention to the lighting system cannot be overemphasized. To prevent progressive  deterioration  of  the  system,  personnel  must provide regular maintenance and prompt repair of any deficiency. Maintain  the  required  illumination  intensity  by keeping lamps, fixtures, and reflective areas clean and in good repair; by replacing defective lamps; and by keeping  the  voltage  steady. It is well known that dirt absorbs and masks light. The  progressive  decrease  of  light  caused  by  accumulat- ing  dirt  renders  periodic  cleaning  of  lighting  equipment a necessity. The frequency of cleaning depends largely upon local conditions. Fixtures in air-conditioned and air-filtered rooms may require cleaning only once a year. In an atmosphere that is heavy with dust and fumes, cleaning every few weeks may be necessary. The cleaning schedule for a particular installation should be determined by light meter readings after the initial  cleaning.  When  subsequent  foot-candle  readings have dropped 20 to 25 percent, the fixtures should be cleaned again. Readings should be made with the light meter at the working surface with the meter reader in the position of the operator or person using the working surface. Lighting  equipment  should  be  washed,  not  just wiped off with a dry cloth. Washing reclaims 5 to 10 percent  more  light  than  dry  wiping  and  reduces  the possibility of marring or scratching the reflecting surface of the fixtures. To clean removable glassware, reflectors, and diffusing  louvers,  immerse  them  in  a  solution  of 5-45