Definition
A supplemental oxygen system that uses an electronic sensor to detect the start of each inhalation and delivers a precisely timed pulse of oxygen only at that moment, rather than supplying a continuous flow. The pulse volume is automatically adjusted for cabin altitude, so the system uses less oxygen at lower altitudes and more at higher altitudes.
Plain English
An oxygen system that gives you a small puff of oxygen the instant you start breathing in, and nothing the rest of the time. It senses each breath and only delivers oxygen when it will actually reach your lungs.
Context Anchor
Seen in discussions of aircraft oxygen equipment, especially systems used by pilots flying at altitudes where supplemental oxygen is needed.
Derivation
The name describes how it works: 'electrical' because an electronic sensor controls delivery, 'pulse' because oxygen is delivered in short bursts rather than steadily, and 'demand' because the system only releases oxygen when the user demands it by inhaling.
Why Pilots Care
It conserves the limited oxygen supply and extends usable duration above 10,000 feet.
Analogy
It is like a motion-sensing faucet: water is not running all the time; it comes on only when the system senses that it is needed.
Intuition Check
Do not read “demand” as meaning the pilot asks for oxygen by pressing a button. In this term, “demand” means the system supplies oxygen when it senses an inhalation.
Example Sentence 1
Before the climb to 17,500 feet, she switched on the electrical pulse-demand oxygen system and confirmed the indicator was pulsing with each breath.
Example Sentence 2
Because the electrical pulse-demand oxygen system only delivers gas on inhalation, the bottle lasted the entire cross-country flight.