What characterizes a recessed sprinkler?

A recessed sprinkler is specifically designed to be installed within a designated recessed housing in the ceiling or wall. This design allows the sprinkler to sit flush with the surface, which not only enhances aesthetic appeal by minimizing visible components but also provides effective fire protection without protruding into the space. The recessed housing allows for proper operation and housing of the sprinkler system while maintaining a neat appearance in the overall design of the interior space.

The other options do not accurately capture the defining characteristics of a recessed sprinkler. For example, while a cover could be involved in the aesthetics, it does not define the sprinkler type itself. Simply hanging from the ceiling implies a standard configuration rather than the specialized recessed installation. Additionally, positioning a sprinkler on the ground is not common in recessed designs and contradicts the very nature of what defines a recessed sprinkler system.