You should check whether the chair would meet at least the following criteria:
Does the seat pan feel comfortable and fit your shape?
The seat pan should not be too long for your legs; otherwise, it will either catch you behind the knees or it will prevent you from leaning fully back against the lumbar support. For clearance, you should have at least a 0.5-inch gap between the front edge of the seat pan and the back of your knees. The seat pan should be long enough to provide you with comfortable support for at least three-quarters of the length of the thigh. Many ergonomic chairs have a adjustable length seat pans to accommodate different body sizes. Most ergonomic chairs have a seat pan with a waterfall front (one that curves down) that prevents the seat from catching you behind the knees. The seat pan should also be contoured to allow even weight distribution and it should be comfortable to sit on. The edge of the seat pan should be soft and contoured so that it cannot cause compression of the thighs and buttocks. The rear of the seat pan should provide comfortable support. You may also want to choose a chair that swivels easily.
Is the seat chair height adjustable?
For preference the chair should be pneumatically adjustable so that you can adjust seat-pan height while you are sitting on the chair. Some chairs have a mechanical height adjustment (spinning) mechanism that is much less convenient to use but is acceptable in some situations. Ideally the chair should height adjust to accommodate a smaller to taller person.
Is the range of height adjustment of the chair sufficient to meet the needs of all users?
You should be able to adjust the height of the seat pan so that the front of your knees is level or slightly below level and your feet are firmly on the ground. In most cases there should be no need for you to use a footrest. The mechanism to adjust seat height should be easy to reach and operate when you are seated.
Does the chair have a comfortable lumbar (lower back) backrest?
Many chairs have cushioned lumbar supports that can be adjusted up and down, that is curved, and that sometimes adjusts forwards and backwards to best fit your lower back shape. If multiple users will use the chair then this type of adjustment may be required. If the chair has a fixed height lumbar support and it feels comfortable when you sit back against this, and you will be the primary user of the chair then a fixed lumbar support may be acceptable.
Is the chair backrest large enough to provide good back support?
Many chairs have back supports that are large enough to provide mid-back and upper-back support to the shoulder-blade level, in addition to good lumbar support. The back of the chair should not interfere with your ability to move your elbows back behind the torso.
When you sit back against the lumbar support is there ample space for hip room?
Insufficient hip room can make you sit too far forwards on the seat pan so that you will not have enough thigh support. When you sit in the chair the seat pan should be at least one inch wider than your hips and thighs on either side.
Does the seat pan still feel comfortable after you've been sitting in it for at least 60–120 minutes?
If the seat pan is made from low-density foam, continuous use can cause it to become permanently deformed and no longer adequate to provide cushioned support. Insufficient cushioning and inappropriate contouring can cause discomfort, imbalance, and hip and back fatigue. Ideally, you should sit in a chair at work for a couple of days to really figure out how comfortable it will be for you.
Does the chair backrest recline and support your back in different positions?
Moving the back while you are sitting helps to maintain a healthy spine. Look for chairs that allow you to easily recline, that provide you with good back support in different recline postures, and that have a back that tracks where your back is. Locking the chair backrest in one position generally isn't recommended or beneficial to users because this restricts the back support that is provided. Research studies confirm the benefits of using chairs that support dynamic sitting rather than encouraging a static posture.
Does the chair have a five-pedestal base?
If chair mobility is important to help you to do your work then the chair should have at least a five-pedestal base with casters that glide freely over the floor surface. Chairs with four casters tip over more easily than those with five casters or more.
Do you need armrests on your chair?
Most ergonomic chairs have armrests, and these should be adjustable. The armrests should be designed to be broad, contoured, cushioned, and comfortable. While sitting you should be able to easily adjust the height of the armrests, and for some situations you should look for adjustable-width armrests that move the armrests closer together or further apart to accommodate different body widths. You should be able to easily move the arms out of the way if you need to do this, for example, when typing or mousing.
Do you need a footrest?
In the vast majority of situations you should not need a foot support to be able to sit comfortably on your chair; however, if you do need a foot support, choose a free-standing, floor-mounted support that allows you to rest your feet out in front of you in a comfortable manner. Resting the feet on the pedestal base of the chair should not be undertaken for prolonged periods because the knee angle typically will be less than 90 degrees, and some restriction of circulation could occur.
What chair covering is best?
Chairs can be covered in a variety of upholstery materials, each of which has benefits and concerns. Vinyl and vinyl-like coverings are easy to clean and spill resistant, but they don't breath, and if the chair begins to heat up under the thighs, uncomfortable amounts of moisture can accumulate. Cloth upholstery is the most common covering, but this is less resistant to spills and more difficult to clean. A cloth-covered seat pan can also become warm and moisture-laden, and cloth-covered foam seat pans can be a significant source of dust-mite allergen. When selecting your chair covering, think about cleaning and maintenance issues and plan appropriately.
Do you need an adjustable-tilt seat pan?
In most situations this is not an essential feature. In some situations it can be helpful to change the tilt of the seat pan to help to maintain a balanced seated posture.