If you are going to use a chair for sitting then purchasing a good chair is very important. Before you purchase a chair following points should be checked:
Seat pan should feel comfortable and should fit your shape
When you sit in the chair the seat pan should be at least one inch wider than your hips and thighs on either side.
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.
The seat pan should also be contoured to allow even weight distribution and it should be comfortable to sit on.
Seat chair height should be adjustable
For preference the chair should be pneumatically adjustable so that you can adjust seat pan height while you are sitting on the chair.
Chair should have a comfortable lumbar (lower back) back rest
Chairs should have cushioned lumbar supports that can be adjusted up and down and forwards and backwards to best fit your shape. If the chair will be used by multiple users then multi level adjustment may be required.
Chair back rest should be large enough to provide good back support
Chairs should have back supports that are large enough to provide mid-back and upper-back support, in addition to good lumbar support.
When you sit back against the lumbar support there should be 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. It will make you tired of sitting very soon.
Seat pan should make you feel comfortable after you've been sitting in it for 60 - 120 minutes
If the seat pan is made from low-density foam then continuous use can cause it to become permanently deformed and then it will not provide adequate cushioned support. Insufficient cushioning and inappropriate contouring can cause discomfort, imbalance and hip and back fatigue.
Chair backrest recline should support your back in different positions
Movement of 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.
Chair should have a 5 pedestal base
If chair mobility is important then for the stability it should have at least a 5 pedestal base with casters that glide freely over the floor surface. You may also want to choose a chair that swivels easily.
Consider the presence of Armrests in your chair
For comfortable sitting, presence of armrests is must. If so, armrests should be broad, contoured, cushioned and comfortable.
Chair covering should be good
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,.
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.