1. Seat pan comfort and shape-When you sit in the chair the eat 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.

2. Think adjustable-You should be able to adjust the height of the seat pan so that the front of your knees are level or slightly below level and your feet are firmly on the ground.

3. Lumbar support is key–Many chairs have cushioned lumbar supports that can be adjusted up, down, forwards and backward to best fit your shape. If the chair will be used by multiple uses then this level of adjustment may be required.

4. Don’t forget about the hips-A chair that doesn’t provide enough hip room can make you sit too far forward on the seat pan, which means that you will not have enough thigh support.

5. Have a long-term strategy- Think about how the chair will feel after 60-120 minutes.  Low-density foam seat pans can become permanently deformed after long-term use which can affect cushioned support leading to discomfort, imbalance, and hip and back fatigue.

6. Chair covers 101-Vinyl and vinyl-like coverings are easy to clean and spill resistant, but they don’t breathe 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 mites allergen. When selecting your chair covering, think about cleaning and maintenance issues and plan appropriately.

https://chiropractic.on.ca/self-management/top-5-tips-selecting-office-chair/