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Ergonomic guidelines for office chairs - backrest width
What others have said about backrest width

National Occupational Health and Safety Commission "The upper limit of 400 mm is based on the criterion of avoiding restriction to elbow movements during keyboard work. An increasing number of office workers are required to use a computer, so this feature is increasingly necessary."


Sydney University ergonomics guidelines "The backrest width should not impede keying posture by causing the arms to be held out to the side"
Australian National University ergonomic guidelines June 2001 "(5) Backrest dimensions:- The backrest should be designed so that it is unlikely to interfere with arm movements. The maximum dimensions of the backrest should be as follows:
  • Width: 360mm; · Height: 430mm" 
BIFMA Ergonomic Guidelines (not free) "The width of the backrest should provide adequate support for the curvature of the user's back without causing localised pressure points." 

BIFMA is the "Business and Institutional Furniture Manufacturer's Association". The BIFMA Ergonomic Guidelines do not take into account the risk that the backrest will interfere with free movement of the elbows. 

I wrote to BIFMA about this, but they did not reply. 

 
Xerox 1993 ergonomic guidelines In this detailed document on workstation design, Xerox specified, based on a long list of references: 

"Backrest width: 12 - 14 inches (30 - 36 cm)."

The current Australian Standard for office chairs was developed by an Australian industry body (similar to BIFMA). As a result, the Australian standard for office chairs now recommends chairs that are quite wrong for small women performing keying tasks. 

What happened? A change has been introduced into office chair standards by chair manufacturers without anyone noticing. The only people who support the present wide backrests are the chair makers, but in a total failure of policy, they have managed to take charge of standard setting!