Adequate space should be allowed between the back (user's position) of a desk or console and any surface or fixed object behind the user for the user to get into and out of a chair freely or to turn in the chair to view the equipment behind.
Additional Information:
A minimum separation of 36 inches from the back of any desk to any opposing surface is suggested as the minimum (see Figure 12.1). A greater separation is preferable. Lateral space for a seated user should be no less than 30 inches; greater latitude is preferable. Placement and spacing of equipment depends on control room configuration, staffing, and other design features. Thus, guidelines are stated in terms of minimum spacing considerations for common equipment arrangements and use situations. Maintenance and testing of equipment has not been considered, and may require larger clearances than the minimums suggested.
Figure 12.1 Spacing of equipment to accommodate seated users.