Final answer:
Appliances with refrigerants that sublimate at atmospheric pressure, like CO2, can be evacuated to atmospheric levels. This aligns with environmental regulations and avoids liquid refrigerant release.
Step-by-step explanation:
Appliances containing refrigerants can be evacuated to atmospheric pressure rather than sub-atmospheric pressures when the refrigerant being used sublimates at standard atmospheric pressure, similar to how carbon dioxide (dry ice) sublimates at 1 atm.
This property of sublimation allows the refrigerant to transition from solid to gas without passing through the liquid phase. In these conditions, refrigerant recovery to atmospheric pressure is sufficient as there is no risk of liquid refrigerant being released, which can happen if it were under pressure.
This is in line with regulations that aim to prevent the release of refrigerants into the atmosphere due to their potential environmental impact, particularly on the ozone layer and in terms of global warming potential. Refrigerant recovery processes are important in the maintenance, servicing, and disposal of refrigeration and air conditioning equipment, and must be done in accordance with environmental regulations.