For what refrigerant is an equipment room refrigerant detector not required under ASHRAE Standard 15 provided the mechanical ventilation system in the machinery is run continuously?

An equipment room refrigerant detector is not required under ASHRAE Standard 15 for refrigerant R-717 (ammonia) if the mechanical ventilation system in the machinery room operates continuously. This is because R-717 is less dense than air and quickly disperses in the atmosphere. Continuous mechanical ventilation helps to minimize the risk of ammonia accumulation, making the environment safer for personnel.

ASHRAE Standard 15 outlines safety standards for refrigerants and their use to protect against potential hazards, primarily focused on their physical properties and potential toxicity levels. With R-717, while it does require careful management due to its toxicity at certain exposure levels, the provision for continuous ventilation reduces the need for a detection system.

In contrast, the other refrigerants mentioned (R-22, R-410A, and R-134A) have different safety profiles and are typically subject to more stringent requirements regarding the detection of leaks, especially in confined spaces. The distinction in requirements underscores the importance of understanding the characteristics of various refrigerants and their behavior in a controlled environment.