Which NFPA standard is focused on sprinkler systems in one- and two-family dwellings?

The correct answer is NFPA 13D, which specifically addresses the installation of sprinkler systems for one- and two-family dwellings. This standard provides guidance for the design and installation of automatic sprinkler systems that are intended to enhance the safety of these residences while considering practical aspects like water supply, system layout, and overall effectiveness in controlling or extinguishing a fire.

NFPA 13, on the other hand, is a comprehensive standard that applies to the installation of sprinkler systems in a wide range of buildings, including commercial properties, but it is not specifically tailored for residential settings. NFPA 13R also pertains to sprinkler systems in residential buildings but is focused on multi-family dwellings with more complex requirements than those in NFPA 13D. NFPA 20 is aimed at fire pump systems and does not directly relate to sprinkler installations in residential properties.