A method and apparatus for ensuring a user to change a filter dryer of a refrigerant recovery unit having a refrigerant determining module that is configured to determine a condition of the refrigerant or an amount of refrigerant that has passed through the filter dryer, or a condition of the filter dryer, an alert device that notifies the user to change the filter dryer in response to the condition, a pressure module that regulates the pressure in the filter dryer, and a pressure-sensing device that is configured to detect a change of pressure in response to filter dryer maintenance. The refrigerant recovery unit is disabled from recovering refrigerant when the refrigerant determining module determines that the filter dryer needs to be replaced, and it is activated in response to the change of pressure detected by the pressure-sensing device.