A gas charging line, or refrigerant charging line, is a flexible hose used to connect a refrigerant cylinder to an AC system for the purpose of adding or removing refrigerant gas. These lines are typically color-coded (blue for low pressure, red for high pressure) to help technicians avoid errors when connecting to the correct ports on the AC unit.

AC system uses a vacuum pump to remove air and water vapor from the system while it's being installed or undergoing maintenance. The vacuum pump is important because if refrigerant reacts with the water vapor and air in your system, the acid produced will corrode its components.

In fact, copper pipe fittings are mainly used with copper pipes used for supplying hot and cold water in residential water supply lines, as refrigerant line in HVAC, etc.

Air conditioners typically use refrigerants like R-410A or R-32, which are Hydrofluorocarbons (HFCs). R-410A is commonly used, while R-32 is gaining popularity due to its lower Global Warming Potential, according to Bajaj Finserv and FreQuip Rentals. Older ACs might use R-22, also known as Freon.

R-134a is a hydrofluorocarbon (HFC) refrigerant used in various refrigeration and air conditioning systems, including automotive air conditioning, household refrigerators, and industrial chillers.

R-22 – also known as Chlorodifluoromethane – is a colorless gas that is commonly used as a refrigerant.

R-410A is a hydrofluorocarbon (HFC) refrigerant gas widely used in air conditioning and heat pump systems.

R290 and R32 are both gases used in air conditioning units. They're also known as refrigerants, which means they help cool down your room by turning into liquids when pumped through the system.

Refrigerant Gas R404A is a colorless odorless mixture of three hydrofluorocarbon compounds in near-azeotropic proportions.