Updated October 2026. Competitor specifications come from each seller’s published pages and manuals, retrieved September 2026, and may change.
What is the difference between PEM and lye-based hydrogen generators?
A PEM generator splits distilled water across a proton exchange membrane and delivers hydrogen separately from oxygen. A lye-based machine electrolyzes water containing sodium hydroxide that the owner mixes, and its output is an unseparated blend of roughly two-thirds hydrogen and one-third oxygen. The practical differences are what comes out, what you handle, and how you maintain the machine.
How does a PEM hydrogen generator work?
A PEM (proton exchange membrane) cell uses a polymer membrane between platinum-coated titanium electrodes. When distilled water is introduced and current is applied, hydrogen ions pass through the membrane and recombine into hydrogen gas on one side, while oxygen is produced on the other. Hydrogen and oxygen are generated and delivered separately, and the only fluid in the machine is distilled water. Revive’s HYD generators use a DuPont PEM, with hydrogen exiting through dedicated hydrogen ports and oxygen through its own port.
Independent laboratory testing (QTT, June 2023) measured 99.992% hydrogen purity on the generator platform used in the HYD line. For what that figure does and does not mean, see Hydrogen Purity: What Does 99.99% Mean?
How does a lye-based hydrogen generator work?
Lye-based machines such as the AquaCure AC60, PureONE, and Promolife H2 System use alkaline electrolysis. The owner mixes a sodium hydroxide (NaOH) electrolyte, for example about 80 g in a liter of distilled water for the AC60 or about 70 g for the PureONE, or adds a dry electrolyte packet to the generator (Promolife). Electrolysis produces hydrogen and oxygen that leave the machine as a single mixed stream, about two-thirds hydrogen.
Because lye vapor can travel with the gas, these machines include a humidifier or purifier cups whose stated job is to capture residual electrolyte mist before the gas reaches you. Their manuals call for gloves and eye protection when handling the electrolyte, and describe periodic draining, rinsing, and (for septic systems) neutralizing used solution before disposal.
PEM vs. lye: side-by-side
| PEM (Revive HYD-1500) | Lye-based (AquaCure AC60) | |
|---|---|---|
| Gas output | Hydrogen and oxygen generated and delivered separately | Unseparated hydrogen/oxygen mix |
| Hydrogen at maximum | 1,000 mL/min (600 / 900 / 1,000 adjustable) | ~660 mL/min (about 66% of ~1,000 mL/min total) |
| Electrolyte | Distilled water only (TDS 5 or less) | Distilled water plus customer-mixed sodium hydroxide |
| Setup and upkeep | Fill with distilled water; drain and refill every 60 hours of use or monthly | Mix electrolyte; periodic drain, rinse, and disposal; gloves and eye protection per manual |
| Power draw | 375 W | ~240-250 W |
| Weight | 32 lbs | 16 lbs |
| List price | $3,299 | $2,999 ($3,399 dual-voltage) |
| Warranty | 3-year limited warranty | “Lifetime” for the original purchaser, with defined exclusions |
Where do lye-based machines make sense?
Lye-based machines have genuine advantages: lower sticker prices, lighter weight, and lower power draw. Promolife is made and assembled in the USA, and PureONE is made in Canada. AquaCure and PureONE offer lifetime warranties with defined scope. If you are comfortable handling and disposing of a caustic electrolyte, and a mixed gas stream does not concern you, these are reasonable options. The trade-offs are the unseparated output and the upkeep.
Does gas separation change the hydrogen dose?
Not by itself. What matters for dose is the fraction of inspired hydrogen (FiH₂), which a 2026 modeling paper (LeBaron et al.) places in a practical window of about 1-4%, and which depends on how much hydrogen reaches your airway, not on total gas flow. The same paper estimates that the oxygen in mixed-gas machines at typical flows raises inspired oxygen only from about 21% to about 21.4%, and found no evidence that oxyhydrogen works better or worse than pure hydrogen at the same FiH₂.
That makes the practical case for PEM less about a different dose and more about what you handle, what you can adjust, and how much hydrogen you actually get per dollar. Because the lye machines’ output is about one-third oxygen, their rated total flow overstates the hydrogen delivered. See our price guide for hydrogen output per machine.
Frequently asked questions
Is PEM better than lye-based electrolysis for hydrogen inhalation?
They differ in what comes out and what ownership involves. PEM machines use only distilled water and deliver separated hydrogen. Lye-based machines cost less up front and weigh less, but use a customer-mixed sodium hydroxide electrolyte and deliver an unseparated gas mix. Which is better depends on your comfort with handling lye and how much you value adjustability.
Do PEM hydrogen generators need chemicals?
No. A PEM generator runs on distilled water only. Revive’s HYD line requires distilled water with a TDS of 5 or less; there is no electrolyte to mix, measure, or dispose of.
Can lye reach the gas you breathe?
Lye-based manufacturers address this with a humidifier or purifier cups designed to capture residual electrolyte mist, which indicates it is a known consideration in that design. A PEM generator uses no lye, so there is none to carry over.
Which type is easier to maintain?
PEM maintenance is distilled water and a scheduled drain-and-refill. Lye-based maintenance includes mixing and replacing electrolyte, handling it with gloves and eye protection, and disposing of used solution, with extra steps for septic systems.
Are both types safe?
Both produce combustible hydrogen and should be used as the manual directs. Research suggests keeping inspired hydrogen at or below about 4%, since higher concentrations in air carry a flammability concern. Hydrogen can also trigger false alarms on electrochemical carbon monoxide detectors.
See the Revive HYD generators
Revive Hydrogen sells the HYD-1500, HYD-1800, and HYD-3000, manufactured by Olive Electronic Technology in Zhengzhou, China, each with three selectable flow settings and a 3-year limited warranty. Compare them on the model comparison page, browse the generators, or download the free Beginner’s Guide to Hydrogen Inhalation.
Related reading: Hydrogen and Cellular Health · Professional vs. Cheap Hydrogen Generators · Hydrogen Inhalation vs. Water
Source: LeBaron TW, Ohno K, Salomez-Ihl C, et al. Respiratory-physiology modeling of therapeutic hydrogen inhalation: defining the fraction of inspired hydrogen (FiH₂) and flow-rate requirements. Respir Res. 2026;27:259. doi:10.1186/s12931-026-03664-9
These statements have not been evaluated by the Food and Drug Administration. This product is not intended to diagnose, treat, cure, or prevent any disease.
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