Which of the following conditions allows the use of a dry standpipe?

A dry standpipe system is specifically designed for use in environments where the piping is subject to freezing temperatures. This system contains no water in the piping until it is needed during a fire emergency. By keeping the standpipe dry, it prevents the water from freezing within the pipes, which could block the system and render it ineffective when it is needed most.

In contrast, using a dry standpipe in non-frozen environments would not make sense, as there is no risk of freezing that necessitates this type of system. Annual system testing is important for all types of standpipes but does not dictate the conditions under which a dry standpipe is appropriate. A fire department may have input regarding standpipe systems; however, their request alone does not determine whether a dry standpipe is required—it's primarily the environmental conditions that dictate this decision. Thus, the correct choice emphasizes the importance of protecting the standpipe from freezing, ensuring reliability and effectiveness in emergency situations.