Inside the machine
An inhaler is three things in a case: a water reservoir, an electrolysis stack, and the electronics that regulate current and monitor the cell. Distilled water enters the stack, direct current is applied across the membrane, and water splits into hydrogen at one electrode and oxygen at the other.
In a PEM/SPE design the solid polymer membrane physically sits between those two half-reactions. That is what allows the hydrogen to be collected as its own stream rather than as a hydrogen-oxygen mixture, and it is why the system runs on plain distilled water instead of a caustic liquid electrolyte.
What flow rate actually means
Flow rate is quoted in millilitres per minute and describes the volume of gas delivered to the cannula. A 900 mL/min system delivers 900 millilitres of hydrogen every minute; a 3000 mL/min platform delivers a little over three litres.
The trap is mixed-gas marketing. If a machine produces an undifferentiated H₂/O₂ mixture, roughly a third of that quoted volume is oxygen by volume. A “1500 mL/min” mixed-gas number is therefore not comparable with 1500 mL/min of separated hydrogen. Always ask which figure is being quoted.
Delivery through the cannula
The gas leaves the machine through a humidifier bottle, which adds moisture so the stream is comfortable over a long session, then travels to a single or dual nasal cannula. Dual cannulas split the same total flow across both nostrils; they do not increase output.
Because hydrogen is the lightest gas there is, tubing runs and connections matter less for flow resistance than they would for oxygen, but they matter a great deal for leaks. Replacing cannulas on schedule is the single most common maintenance item owners overlook.
What a session looks like
Most owners run twenty to sixty minutes, seated, doing something else. There is no sensation to chase: hydrogen is odourless and non-irritating, so the session feels like nothing in particular, which surprises people who expect an oxygen-concentrator-style experience.
Fill with distilled water only. Tap and mineral water leave deposits that shorten cell life and can trigger conductivity warnings on the console.
Choosing an output level
Lower-output units suit a single user with a fixed daily slot. Higher-output platforms suit longer sessions, multiple household users, or a practitioner setting where the machine runs most of the day. Duty cycle and thermal headroom separate these classes more than the headline number does.
Whatever the class, treat purity and certification data as hardware facts. They describe what the machine builds and emits, not a medical or therapeutic status.