Chairs should be designed to adjust for and accommodate several factors:
Seat Height: Seat height should be pneumatically adjusted while seated. A range of 16 – 20.5 inches off the floor should accommodate most users. Thighs should be horizontal, lower legs vertical, feet flat on the floor or on a footrest. Seat height should also allow a 90 degree angle at the elbows for typing.
Seat Width and Depth: A seat width of 17-20 inches suffices for most people and should be deep enough to permit the back to contact the lumbar backrest without cutting into the backs of knees. The front edge should be rounded and padded. The seat slant should be adjustable (0 to 10 degrees). Avoid bucket-type seats. The seat should swivel easily.
Backrest: The backrest should offer firm support, especially in the lumbar (lower back) region, should be 12-19 inches wide, and should be easily adjustable both in angle and height, while sitting. The optimum angle between seat and back should permit a working posture of at least 90 degrees between the spine and thighs. Seat pan angle and backrest height and angle should be coordinated to allow for the most comfortable weight load on the spinal column.
Seat Material: A chair seat and back should be padded enough to allow comfortable circulation. If a seat is too soft, the muscles must always adjust to maintain a steady posture, causing strain and fatigue. The seat fabric should “breathe” to allow air circulation through clothes to the skin.
Armrests: Armrests are optional, depending on user preference and task performed. They should not restrict movement or impede the worker’s ability to get close enough to the work surface. The worker should not rest his or her forearms while keying.
ERGONOMIC CHAIR CHECKLIST
1. Chair has wheels or castors suitable for the floor surface
2. Chair swivels
3. Backrest is adjustable for both height and angle
4. Backrest supports the inward curve of the lower back
5. Chair height is appropriate for the individual & the work surface height
6. Chair is adjusted so there is no pressure on the backs of the legs, and feet are flat on
the floor or on a foot rest
7. Chair is adjustable from the sitting position
8. Chair upholstery is a breathable fabric
9. Footrests are used if feet do not rest flat on the floor