A well-designed chair will help maximize operator productivity while reducing the incidence of lower-back-related health problems. In general, a workstation chair should meet all the following criteria:

Number of legs: The chair should have five legs for structural stability. It should be on casters if the operator alternately sits and stands, or if they frequently move about at the workstation. If workers must place or obtain materials to or from their side, the chair should swivel to prevent upper body twisting.

Seat Height: The height of the chair seat should be adjustable, usually between 15 and 21 inches from the floor for primarily sitting tasks. For alternate sit / stand workstations, the chair height should be compatible with the height of the work surfaces, so the person's upper body (normally their elbows) remain at the same height above the floor whether they are sitting or standing.

Footrests: If the seat height is more than 18 inches from the floor, footrests should be provided. They should have a nonskid surface, be 12 to 16 inches long, and slope 30 degrees or less.

• The seat cushion should be firm but not hard and preferably of some non-slip fabric type material. This will help reduce the buildup of body moisture.
  
• The seat cushion should be slightly hollowed (i.e. concave).
  
• The front edge of the seat cushion should curve downward. This facilitates good blood circulation to the feet because it reduces the pressure on the underside of the thighs.
  
• The seat cushion should be about 18 inches across and 16 inches from front to rear (plus or minus one inch).
  
• The seat cushion should usually be horizontal. However, adjustable backward tilts of zero to eight degrees have proven beneficial in shifting the body's weight against the backrest.
  

Backrest: The backrest should be between 13 and 18 inches wide and be easily adjustable between four and nine inches above the seat cushion. If the backrest is nonadjustable, is should start no higher than four inches above the seat cushion and extend upwards about 18 inches.

Arm rests: For primarily physical work tasks, the chair should NOT have arm rests because they tend to restrict the natural movement of the arms. For primarily nonphysical work tasks (such as clerical duties), the arm rests should be at least 19 inches apart, nine inches above the seat cushion, and about three inches wide (plus or minus one-half inch).

Training: The user of the chair should receive the benefit of a training session in how to adjust the chair. Ideally, no tools should be required to make adjustments, so each operator can easily find the most comfortable position for them through trial and error.

Finally, no single chair is optimal for all work tasks. The chair's design should be matched to the overall functional design of the workstation and to the tasks being performed at the workstation.