Final answer:
Technicians must evacuate an appliance containing 10 lb of CFC-500 to 4 inches of mercury vacuum. The disposal process is critical in compliance with the Montreal Protocol's efforts to phase out ozone-depleting substances such as CFCs and promote ozone layer recovery.
Step-by-step explanation:
The question concerns the proper evacuation levels for disposing of appliances containing chlorofluorocarbons (CFCs), specifically CFC-500, when using recovery and recycling equipment manufactured before November 15, 1993. According to U.S. EPA regulations, before disposing of an appliance containing 10 lb of CFC-500, technicians must evacuate the refrigerant to 4 inches of mercury vacuum. This measure is a means to reduce ozone-depleting substances from being released into the atmosphere.
In a broader context, this ties in with environmental protocols such as the Montreal Protocol, an international agreement aimed at phasing out the production and consumption of ozone-depleting substances (ODS), including CFCs. Since the ratification of this protocol, there has been a significant decline in the emission of ODS, and the ozone layer is showing signs of recovery. However, constant vigilance and adherence to regulations remain essential, as illegal production and use of ODS can threaten the rebuilding of the ozone layer.