System-dependent recovery methods are permitted only on appliances containing what maximum amount of refrigerant?

The correct answer is based on regulations set by the Environmental Protection Agency (EPA) regarding refrigerant recovery methods. System-dependent recovery methods are specifically allowed for appliances that contain 15 pounds or less of refrigerant. This limitation exists because system-dependent recovery systems rely on the existing system pressure to facilitate the recovery of refrigerants, and this method is not suitable or safe for larger quantities as it could lead to inefficiencies or potential harmful situations if the system fails or does not recover all the refrigerant.

When an appliance contains more than this threshold, the use of self-contained or active recovery equipment is mandated to ensure complete and safe recovery of refrigerants, which helps to prevent emissions into the atmosphere, addressing concerns regarding ozone depletion and global warming. Hence, the significance of the exact threshold of 15 pounds stands to emphasize the necessity of stringent safety measures and proper handling of refrigerants in larger quantities.