HVAC sysyem is used for Heating and cooling of a Device which is electronically used for specific puposes.
For Heating or cooling of a device special types of gases are used in to these devices which maintains the temperature of a particular space by using R12 type of gases.
These gases are costly and for recovery of this type of gases A [https://www.refrigerantrecoverymachine.com/|Refrigerant Recovery Machine] is used.