Within sprinkler protection zones, are shadow areas allowed to remain dry?

• A. No, all areas must be wet.
• B. Yes, dry areas within protection zones are allowed.
• C. Only if the area is less than 2 ft².
• D. Only in storage rooms.

Answer: (B)

Within a sprinkler protection zone, some portions of the space may not be reached by water spray because of obstructions or the geometry of the spray patterns. Those pockets are called shadow areas. In NFPA 13R for low-rise residential systems, it is acceptable for these shadow areas to remain dry. The protection zone as a whole relies on the surrounding wetted areas and multiple heads to control a fire, so a small dry pocket inside the same zone does not negate the intended protection. This approach helps balance effective fire control with practical system design, without requiring every tiny nook to be wetted immediately.