A patient control mechanism is provided for an air conduit circuit that has a dental unit, a foot control and a compressed air source. The mechanism consists of a first valve disposed within the air conduit circuit between the dental unit and the foot control, a second valve directly connected to the first valve and a third valve disposed within the air conduit circuit between the dental unit and the second valve. A patient can manually control the third valve by sending an air signal to the second valve which operates the first valve deactivating the dental unit if pain is felt by the patient.