Definition
A fitting installed in an aircraft oxygen system that allows a passenger to receive a continuous flow of oxygen from a standard-pressure source for medical or therapeutic purposes, rather than the on-demand or diluted flow normally supplied to crew and passenger masks.
Plain English
A connector that lets a passenger who needs medical oxygen plug their own mask into the aircraft's oxygen system and get a steady flow of pure oxygen.
Context Anchor
Seen in aircraft oxygen equipment descriptions, first-aid oxygen kits, and maintenance checks involving oxygen masks, hoses, and outlets.
Derivation
Therapeutic comes from the Greek 'therapeutikos,' meaning 'serving to cure or heal.' The word signals that this adapter is for medical use by a passenger, not for routine flight-crew oxygen supply.
Why Pilots Care
If a passenger boards with a medical oxygen requirement, the pilot needs to know whether the aircraft's oxygen system has a therapeutic mask adapter and how it is used. Without it, the aircraft's standard masks may not deliver oxygen in the steady form the passenger needs.
Analogy
It works like a plug adapter: the oxygen mask and the oxygen outlet may not fit each other directly, so the adapter makes the connection possible.
Intuition Check
Therapeutic does not mean relaxation or comfort here. It means oxygen being given for a medical or first-aid need.
Example Sentence 1
Before the flight, the captain confirmed that the therapeutic mask adapter was installed and working so the passenger could use her own medical oxygen mask.
Example Sentence 2
During the oxygen equipment check, the mechanic verified that the therapeutic mask adapter seated properly on the regulator outlet.