Final answer:
A supply of at least six spare sprinkler heads should be kept near the sprinkler riser room or where sprinkler controls are located, in a readily accessible area.
Step-by-step explanation:
A supply of at least six spare sprinkler heads must be kept available on the premises in an area that is readily accessible and near the sprinkler riser room or the area where sprinkler controls are located. This is to ensure that in case any of the active heads fail or there is a need for replacement, there is no delay in performing the necessary maintenance. The location should be chosen carefully to prevent potential accidents and to ensure that the spare sprinkler heads are protected from damage. It's important to know where specific safety equipment is located, such as fire extinguishers and eyewash stations, and the same goes for maintaining a stocked inventory of critical system components like sprinkler heads.