On the plan sheet P01, the fire protection symbols that are square with a solid dot typically represent a recessed pendent sprinkler head designed for ordinary temperature, quick response. This symbol is used in NFPA standards, particularly in NFPA 13, to indicate sprinkler types and their installation characteristics.
Recessed pendent sprinklers are installed to protect against fire hazards from the ceiling downwards, and their quick response mechanism helps to control fires rapidly in occupied spaces.