Chair Buying Guidelines
The chair may be the single most important piece of office equipment that you buy. Although individual preferences are certainly part of choosing a chair, the following are essential features that should be evaluated before a new chair is purchased.

1. Lumbar support. When people sit down the lumbar curve flattens out, increasing the compressive force on the intervertebral discs. The lumbar support should be positioned at about the belt level and should feel comfortable as well as support the lumbar curve in the seated position.
2. Seat pan height adjustability. The rule of thumb is that the seat pan height should be approximately the same distance from the floor that the creases at the back of your knees are. This distance will change with the height of the heel on your shoes, and you should be able to adjust the chair height accordingly.
3. The seat pan length. The length of the seat pan should correspond with the length from the back of the knees to the buttocks of the person sitting in the chair. Differences in seat pan length can be achieved by making the chair in different sizes, or by designing the chair so that the seat back can be adjusted forward to shorten the seat pan length or backward to lengthen the seat pan length.
4. Arm rests. Arm rests should be adjustable both in and out and up and down. The arm rest should support the elbow and forearm when the arm is in the neutral position. The neutral position for the arm is at the side of the trunk. If the arm rests do not fit the person using the chair it is better not to have arm rests.

Other features that are essential in an ergonomically designed chair include:
a five-point base
a waterfall edge to the front of the seat pan
supportive cushioning
breathable upholstery material.
Many chairs come with a 10 year warranty that can offset a higher initial price. Of course, the chair should be of overall good quality and the controls should be intuitive and easy to use.

Additional features to consider:
* seat pan tilt - by changing the tilt of the seat pan the angle between the thighs and the back opens up and decrease the compressive force on the intervertebral discs
* seat back angle - another way to open up the angle between the thighs and the back is to adjust the seat back so that the user can lean back in the chair. This posture is usually not comfortable for extensive keying but can be used while reading material or talking on the phone. The change in posture relieves decrease the accumulated physiological and musculoskeletal stress.