The issue of computer terminal safety keeps being raised in letters to the contributing editors. The most recent query resulted from a union complaint brought against a university in the Northeastern United States.
The editors know of no scientific study which has established a safety risk with regard to computer terminals or PCs, regardless of the number of hours per day of use. There are several studies which document discomfort due to the improper placement of the equipment, poor chair height and angle, and long periods of use without a break. This discomfort is cumulative and thus becomes increasingly more painful if no relief is provided. One of the most useful studies to date was that done by the Buffalo Organization for Social and Technical Innovation (BOSTI) in 1984. That study, among other things, established a direct correlation between operator discomfort when using a computer terminal and low productivity. Thereby concluding that it is in the economic interest of organizations to be responsive to complaints of discomfort.
Not surprisingly, the most common discomfort reported is eyestrain, with symptoms ranging from bloodshot eyes to bad headaches. Eyestrain very often is caused by the improper placement of the equipment so that reflected light causes screen glare. An obvious solution is to turn the terminal or PC screen away from a window which causes the glare, or away from a light fixture which may reflect on the screen. If funds permit, the white prismatic light lens common on fluorescent fixtures can be replaced with smaller parabolic cell lenses--lenses which hide the tubes while directing the light downward. There also are a number of anti-glare filters which can be affixed to terminal screens. It is also highly desirable to reduce the contrast between the desk surface and the papers and other materials with which a person is working. Dark walnut finishes On desk tops produce a contrast in the range of 15:1, while light oak finishes produce contrast around 3:1. The lower the ratio, the less discomfort to the eyes. When there is an opportunity to design new space, parabolic reflectors and light-colored work surfaces should be specified to provide optimum lighting for those working at computer screens.
Another common error is to place equipment on standard desk tops which are too high--usually 29 inches or higher-- or continuing to use old equipment which integrates the keyboard and the screen in a single device rather than providing a separate keyboard. It is essential that an individual be able to adjust the eye distance and the arm distance separately.
Poor chair height and angle are also common. If secretarial chairs are used--as generally is recommended--they should be adjusted for each operator rather than remaining on the same setting all of the time. Administrators should be sure that a chair seat's height can be adjusted between 16 and 20 inches, that the back support height is also adjustable, that the seat- back tilt can be locked in a variety of positions, and that the chair provides both lumbar and dorsal back support, and that these adjustments are easy to make. The operator can best determine what the most comfortable setting is for him or her.
Uninterrupted use of the terminal or PC for more than 2 hours is not recommended, Ideally, a person should spend no more than 6 hours a day at a terminal or PC screen. If longer periods are necessary on some days, it is desirable that the individual take frequent short breaks by focusing on some object at least 15 feet away for a few minutes, getting up from the terminal or PC and walking a short distance, or interspersing terminal time with other tasks.
The subject of computer terminal safety continues to be studied, with current attention being focused on radiation. Every one of the more than a dozen published studies to date concludes that none of the terminals or PCs pose a problem. New units appearing in the market are constantly being tested, especially those produced in third world countries.