What level of mercury evacuation is required for External Recovery Tanks before they can be put in service?

The correct level of mercury evacuation required for External Recovery Tanks before they can be put in service is 27 inches. This evacuation level is essential to ensure that the recovery tanks are capable of safely holding the refrigerant without the risk of release into the atmosphere. Achieving this level ensures that the tanks are devoid of air and moisture, which can cause contamination and affect the integrity of the refrigerant being recovered.

Setting the evacuation standard at 27 inches also reflects industry best practices as established by regulatory guidelines. By reaching this vacuum level, technicians can be confident that the tank is appropriately prepared for use in recovering refrigerants, ultimately adhering to environmental regulations that aim to minimize potential harm from refrigerant leaks and promote safe handling of these substances.

In contrast, levels set above or below this requirement may either compromise safety protocols or not adequately prepare the recovery tanks for efficient refrigerant management.