When are listed guards required for sprinklers?

Listed guards are required for sprinklers primarily when they are subject to mechanical injury. This requirement is rooted in the need to protect sprinklers from potential damage that could impair their function in an emergency. Sprinklers are critical components of fire protection systems, and any damage could hinder their ability to discharge water effectively, compromising safety.

Mechanical injury can come from various sources, including physical collisions, impacts from vehicles, or wear and tear from daily activities in spaces where sprinklers are installed. The use of listed guards ensures that the sprinkler heads are shielded from such hazards while still allowing them to operate effectively in the event of a fire.

The other options, while relevant in specific contexts, do not universally necessitate the use of listed guards. For example, outdoor installations may require other considerations like environmental factors, but not specifically guards solely based on being outdoors. High-traffic areas may increase the likelihood of mechanical injury, but the requirement for listed guards is not limited to just these scenarios. Similarly, the status of being new does not dictate whether guards are necessary; it's the risk of mechanical damage that triggers the requirement.