In much of this chapter, there is no special mention of which refrigerant is being assumed. The fact is, however, that safety requirements are heightened for ammonia. Certainly, all the specifications in ANSI/ASHRAE Standard 15–
94 dealing with the testing and protection of pressure vessels are equally applicable to all refrigerants. But the appreciably lower concentration considered toxic for ammonia compared to that for most of the halocarbons, as pointed out in Chapter 12, reinforces the need for special care, and attention to safety details in ammonia systems.
Unique precautions, however, also apply to halocarbon systems. In a large halocarbon plant, a significant quantity of refrigerant could escape without the operators being aware of it, because halocarbons are odorless. A further characteristic of halocarbons is that they are heavier than air and may collect in low levels of the building, such as a basement. High concentrations can asphyxiate a worker, so this potentially dangerous situation should be prevented by suitable detectors and alarms. With ammonia, the existence of a leak is evident because of the odor, and the challenge is to control the magnitude and correct the leak to avoid injury to people and damage to products.