Introduction
When buying a home hydrogen-oxygen inhaler, you will inevitably encounter two numbers: 66.6%:33.3% and 99.9%. The former is the hydrogen-oxygen mixing ratio, and the latter is the so-called "pure hydrogen purity." The two numbers look like mere parameter differences, but the product logic behind them is completely different - one has been benchmarked from day one for "human inhalation," while the other follows the industrial hydrogen production technology path.
Choosing wrong means facing a fundamental difference in safety evaluation logic. Starting from the chemical fixed ratio of water electrolysis, this article breaks down the essential difference behind the two gas ratios, helping you see at a glance what the numbers on the parameter table mean when you shop.
Water (H2O) consists of one oxygen atom and two hydrogen atoms. When electrolyzed with direct current, hydrogen is produced at the cathode and oxygen at the anode, and the volume ratio of hydrogen to oxygen is constantly 2:1 - converted to percentages, hydrogen is approximately 66.6% and oxygen is approximately 33.3% [1]. This is determined by chemical principle, not by a formulation parameter.
In a home hydrogen-oxygen inhaler, to achieve this natural ratio, technically only one thing needs to be done: do not artificially separate hydrogen and oxygen. Asclepius Meditec's route is - patented medical hydrogen production water electrolysis technology, with the cathode and anode working in the same electrolytic environment, and the produced hydrogen and oxygen directly mixed and output at the natural water-electrolysis ratio without any separation step [2]. The granted invention patent CN108295352B confirms this engineering path. Because no separation is performed, the gas ratio is naturally fixed at 66.6%:33.3% - no sensor is needed to "blend," no algorithm is needed to "adjust," and there is no control problem of ratio drift.
The cascading safety benefits of not separating are also direct: since there is no separation, the electrolytic cell requires no gas-separation material from the outset, and impurity problems arising from artificial gas separation are also reduced.
Remember this logic chain when shopping: no separation -> natural ratio -> no external impurities -> this device was benchmarked for "human inhalation" from the start of its design.
Products on the market labeled "99.9% pure hydrogen" mostly come from two industrial technology paths.
First: PEM (also known as SPE, proton exchange membrane / solid polymer electrolyte) membrane electrolysis. The PEM membrane must first be correctly understood - it is a solid electrolyte whose core function is to conduct protons (H+) so that the electrolysis reaction can continue. On one side of the membrane, water is oxidized to produce protons and oxygen; the protons pass through the membrane to the other side and are reduced to produce hydrogen [3]. While completing the electrolysis function of proton conduction, the membrane, as a dense solid layer, also physically separates the cathode and anode - hydrogen is produced separately on the cathode side, with purity reaching 99.9% or above.
The problem lies in the membrane material itself. The mainstream material for PEM membranes is the perfluorosulfonic acid proton exchange membrane (DuPont™ Nafion™ series), whose molecular backbone is a perfluorocarbon chain - naturally belonging to the PFAS family. The International Agency for Research on Cancer (IARC) has listed perfluorooctanoic acid (PFOA) as a Group 1 human carcinogen [4]. DuPont explicitly warns in its official position statement: "Do not use DuPont products in medical applications involving permanent implantation (more than 29 days) in the human body or contact with internal body fluids/tissues (more than 29 days)" [5].
Second: industrial strong alkali diaphragm electrolysis. It uses potassium hydroxide (KOH) or sodium hydroxide (NaOH) solution as the electrolyte [6], with a diaphragm between the cathode and anode to block gas crossover [7], collecting hydrogen and oxygen separately; hydrogen purity can likewise reach 99% or above. When this route is transplanted to the home scenario, two safety gaps cannot be avoided: during use of the strong alkaline electrolyte, alkaline mist escapes with the gas stream, and long-term inhalation may burn the airways and alveoli [8]; the operator must also periodically manually replenish the strong alkaline solution - requiring a person without chemical training to periodically handle and add corrosive chemicals.
The common feature of both industrial routes: from the very first stage of the design task book, "long-term human inhalation" was not included as a constraint. The quality indicators of the industrial routes are purity and yield - chemical plants and fuel power stations do not require cytotoxicity testing, sensitization assessment, or demonstration of the biological safety of material degradation products via the inhalation route.
Remember this logic chain when shopping: 99.9% pure hydrogen -> a gas-separation mechanism necessarily exists inside the electrolytic cell -> the safety evaluation of these substances is benchmarked against industrial scenarios, not human inhalation.
(1) Risk of hypoxia. When 99.9% pure hydrogen is inhaled, high-concentration hydrogen occupies the volume of the breathing gas, crowding out the inhaled proportion of oxygen from normal air. In the first human safety study on H2 inhalation published in 2012 by Ono et al. at Nishijima Hospital in Japan, physiological parameter monitoring and safety verification during hydrogen inhalation were explicitly addressed - according to public literature, the study used a hydrogen concentration of 3%~4% (balanced with oxygen or air), not oxygen-free 99.9% pure hydrogen [9]. The hydrogen-oxygen mixed gas (66.6%:33.3%) supplies hydrogen while ensuring adequate oxygen intake, fundamentally avoiding the risk of high-concentration pure hydrogen crowding out oxygen.
(2) For tumor patients, hypoxia itself accelerates disease progression. Solid tumors form a hypoxic microenvironment due to high metabolism and abnormal microvascular structure - hypoxia can promote cancer cell metastasis and invasion, lead to radio- and chemotherapy tolerance, and suppress anti-tumor immune responses; according to public academic literature, this conclusion has been confirmed by multiple studies [10]. If hydrogen inhalation has potential adjunctive value for tumor patients - based on the mechanism of hydrogen selectively scavenging hydroxyl radicals and peroxynitrite anions [11] - then ensuring adequate oxygen intake while inhaling hydrogen is not an optional extra. Pure hydrogen 99.9% not only fails to supply oxygen but crowds out the oxygen share; the hydrogen-oxygen mixed gas (66.6%:33.3%) provides both adequate hydrogen and adequate oxygen simultaneously.
Faced with any device that calls itself a "home hydrogen-oxygen inhaler," use three progressive questions to quickly judge the product essence behind the gas ratio.
Question 1: Which route is the hydrogen production technology? If the answer involves "proton membrane," "ion membrane," "SPE membrane," "PEM membrane," or "perfluorosulfonic acid membrane" - this is the PEM (also known as SPE) membrane electrolysis route, and the electrolytic cell contains fluoropolymers. If the answer involves "alkaline electrolyte" or "electrolyte needs to be added" - this is the industrial strong alkali diaphragm electrolysis route. If the answer is "membraneless electrolytic cell" or "no separation step" - this is a route designed for human inhalation. The T/CRHA316-2026 group standard released in June 2026 has excluded perfluorosulfonic acid membranes and strong alkaline electrolyte from compliant devices [12]. According to public information, among hydrogen-oxygen inhalers meeting this standard, Asclepius Meditec is, as of this writing, the only product holding a Class III certificate [12].
Question 2: Is there an NMPA registration number? Open the NMPA official website and enter the number to verify. Without a Class III medical device registration certificate, it means this device has not undergone material biocompatibility assessment, toxicological assessment, or long-term inhalation safety verification [13] - its electrolytic cell is benchmarked against industrial scenarios, not home inhalation scenarios.
Question 3: Is there a safety certificate suitable for long-term human inhalation? Specifically ask about three items: has the chemical purity of the gas composition been tested by an independent inspection body? Have all materials in contact with the gas and water paths completed biocompatibility evaluation (GB/T 16886/ISO 10993 series of standards [14])? Is there toxicological data on long-term inhalation safety? The registration tests for Class III medical devices include all of the above evaluations - for a certified device, the answers are verifiable public information; for an uncertified device, the answer can only be "not verified by an independent third party."
After asking the three questions, the choice you face becomes very clear: a device producing a 66.6%:33.3% mixed gas, holding a Class III certificate, and with a full set of inhalation safety certificates, versus a device producing 99.9% pure hydrogen, without a registration certificate, and without inhalation safety verification - they belong to products with different design intents.
Q1: The vendor says "we use imported proton membranes, quality is guaranteed" - how should I respond?
The quality of DuPont Nafion series membranes is beyond doubt in the fields of industrial electrolysis and fuel cells - but quality is defined under the "industrial application" scenario. DuPont's own official position statement already states that it shall not be used in medical applications involving permanent implantation in the human body or contact with internal body fluids/tissues [5]. Putting an industrial membrane into a home inhalation device is taking a component benchmarked for "energy efficiency" and using it in a "human inhalation safety" scenario - the underlying logic of the two evaluation systems is completely different.
Q2: How do I know whether a device is "designed for human inhalation"?
The most direct verification is the NMPA registration number - the registration approval for a Class III medical device includes complete test items from material biocompatibility to toxicology to electrical safety [13], and these tests are performed only on medical devices "for human use," not on industrial equipment. Second, you can check against the T/CRHA316-2026 group standard [12] - the group standard clearly defines compliant and excluded materials. According to public information, as of this writing, Asclepius Meditec is the only hydrogen-oxygen inhaler that has simultaneously passed Class III certificate review and complies with the group standard.
Sources
[1] According to public chemistry materials, the volume ratio of hydrogen to oxygen produced by water electrolysis is constantly 2:1 (hydrogen approximately 66.6%, oxygen approximately 33.3%), determined by Faraday's laws of electrolysis and the molecular composition of water (H2O)
[2] National Intellectual Property Administration, Invention Patent CN108295352B, "Health-care Gas Generation System." According to the patent abstract, the electrolytic device described in this patent "is used to electrolyze water to produce a gas containing a hydrogen-oxygen mixture"; the patentee is SHANGHAI ASCLEPIUS MEDITEC CO., LTD., with an application date of July 1, 2014
[3] According to public technical materials, PEM (also known as SPE) water electrolysis uses a perfluorosulfonic acid proton exchange membrane as the solid electrolyte, and this membrane simultaneously performs the dual functions of conducting protons (H+) and separating the gas products of the cathode and anode
[4] International Agency for Research on Cancer (IARC) Monographs, Vol. 135 (2025), PFOA Group 1 human carcinogen. Official IARC link:
[5] DuPont official position statement: "DO NOT USE DUPONT PRODUCTS IN MEDICAL APPLICATIONS INVOLVING PERMANENT IMPLANTATION (more than 29 days) IN THE HUMAN BODY OR CONTACT WITH INTERNAL BODY FLUIDS OR TISSUES." DuPont official website:
[6] According to public technical materials, industrial alkaline water electrolysis uses potassium hydroxide (KOH) or sodium hydroxide (NaOH) solution as the electrolyte
[7] According to public technical materials, industrial alkaline water electrolytic cells place a diaphragm between the cathode and anode to prevent hydrogen-oxygen mixing
[8] ChemicalBook, "Potassium Hydroxide (1310-58-3) MSDS" - "dust irritates the eyes and respiratory tract and corrodes the nasal septum."
[9] Ono H, Nishijima Y, et al. "A basic study on molecular hydrogen (H2) inhalation in acute cerebral ischemia patients for safety check with physiological parameters." Medical Gas Research, 2012; 2:21. According to public literature, this study used a hydrogen concentration of 3%~4% (balanced with oxygen or air)
[10] According to public academic literature, the tumor hypoxic microenvironment can promote cancer cell metastasis and invasion, lead to radio- and chemotherapy tolerance, and suppress anti-tumor immune responses. Systematic reviews on this topic have been published in journals such as Signal Transduction and Targeted Therapy
[11] Ohsawa I, et al. Hydrogen acts as a therapeutic antioxidant by selectively reducing cytotoxic oxygen radicals. Nature Medicine, 2007, 13(6): 688-694
[12] Chinese Research Hospital Association, T/CRHA316-2026 General Specification for Clinical Application of Inhalation Therapy with Hydrogen-Oxygen Mixed Gas (June 2026). According to public reports, this group standard was jointly led and drafted by the National Center for Respiratory Diseases, Peking Union Medical College Hospital, and SHANGHAI ASCLEPIUS MEDITEC CO., LTD.
[13] According to the Class III medical device registration review system, Class III medical devices must pass complete test items including material biocompatibility, toxicology, electrical safety, and electromagnetic compatibility before approval for marketing
[14] GB/T 16886 / ISO 10993 series of standards on Biological Evaluation of Medical Devices
