ERGONOMICS & VDTs
Computer Workstation Design
Ergonomics is the study of the relationship between people and the tools of their occupation. In particular, ergonomics focuses on the physical interface between the worker and the way he or she uses the tools of their job. A tool such as a computer workstation is said to have good ergonomic design when it can be easily adjusted to fit the user. With good ergonomics, the user does not have to contort their body or perform repetitive movements in ways that could cause discomfort, strain, or injury.
Physical Factors Do Affect Worker Performance and Health
Work station design and layout play the most critical role in eliminating postural problems and other sources of injury. Musculoskeletal injury and visual fatigue are the primary concerns associated with computer workstations. Fortunately these can be controlled through proper worksataion design and use.
A first step in ergonomic evaluations is to establish the optimum posture of the operator. This ensures heights and angles of equipment (e.g., chair, table, copy holder, keyboard, monitor, etc.) fit the individual, which in turn helps increase comfort and productivity.
Several physical factors which affect a computer operator's performance and health are described below. The numbered diagram will help you visualize these items.
- The chair should be easily adjustable to provide good support to your lower back and allow up/down movements for proper height interface with the keyboard. The seat pan should have the ability to tilt forward or backward and the chair should be fitted with casters if tasks require the operator to get up or move around the workstation frequently. (Be sure casters selected are appropriate for the type of flooring i.e., carpet vs. vinyl).
- Body posture should be as shown with right angles at the elbow, hip, and knee. The head should be held in a neutral position facing straight ahead with the eyes gazing forward or slightly down.
- A foot rest may be needed when the operator's feet do not comfortably reach the floor, although this should not be necessary if both the table and the chair are height-adjustable. The feet should reach and touch the floor in a flat, relaxed manner. Foot and leg circulation will be affected if over extension of the feet occurs, as is the case when the user wears high-heeled shoes.
- The keyboard support table can be adjusted to allow proper upper body posture, or the chair height can be adjusted to achieve the same purpose. The keyboard should be detachable to permit flexible positioning. A wrist rest should be available for those who desire it. Keeping the wrist level straight and in a relaxed position offers the worker maximum comfort for extended hours of work.
- A document holder should be provided and adjustable in height and angle of tilt, to the same height and plane that the operator views the majority of the time. Usually the position will be at or just below screen level, allowing the operator to hold his/her head in the neutral position shown in the diagram.
- The display monitor (VDT) should be positioned so that the distance from the eye to the screen can be adjusted, allowing the center of the screen to be positioned so viewing angle is 15 to 25 degrees below eye level. Display monitors placed too low will increase musculoskeletal tension and fatigue to the back and neck. Display monitors placed too high will also increase visual fatigue and neck tension. The screen should be detached from the keyboard so that each can be positioned in an optimum manner. If ocular fatigue and/or vision problems are experienced by VDT workers, they should see their ophthalmologist to rule out any need for prescription glasses.
- General lighting for the office and VDT work vary between operators. Light above and behind the display monitor will glare onto the screen. Reduce glare onto the screen by appropriate placement of the display screen in the room. The VDT workstation should be oriented so the operator does not face an unshielded window or a bright light source. The orientation of the video screen should be perpendicular or nearly perpendicular to the line of windows.
The screen should be tiltable to help eliminate screen reflections. Reduce mirror-like reflections on the screen by using an etched screen surface, a thin-film coating, or a hood. Other types of reflections on the screen can be reduced by using a neutral density, micro-mesh, or glare-resistant filter.
- Due to the work demands put on VDT operators, it is important that environmental factors such as temperature (68o to 78o F), humidity (30-70%), and noise (<75 dbA or as low as achievable) be kept within acceptable ranges.
Concerns About Radiation
There has been concern among computer users about the various types of radiation (e.g. X-Ray and ELF) produced by computer equipment. Exposure levels to radiation during computer use is very very low (not significantly above background). There is currently no accepted scientific evidence which suggests radiation exposure from computer use is harmful; however, if this is something you are concerned about, EH&S suggests you practice "prudent avoidance." This is done by staying about an arm's length from the monitor, thereby eliminating almost all of your exposure.
Further assistance and information can be obtained by contacting EH&S at 459-2553.