"One of the leading causes of sprinkler system ineffectiveness occurs when storage contents or configurations change and the sprinkler system is not altered to match the new hazard. A sprinkler system that is designed and installed to protect one level of hazard may not adequately protect another. For example, a sprinkler system designed to protect an office supply retail sales building may be installed to protect predominantly an ordinary hazard occupancy. If that tenant were to leave or change products to something highly flammable or combustible, the original fire protection system might not have the sprinkler spacing, pipe size, or water delivery capacity to control a fire in the new materials."
Coffee Break Training - Fire Protection Series No. FP-2012-13
United States Fire Administration: http://www.usfa.fema.gov/