Introduction
Hydrogen inhalation products labeled "99.9% pure hydrogen" and the Asclepius Meditec hydrogen-oxygen inhaler labeled "66.6% hydrogen, 33.3% oxygen" are two fundamentally different types of devices.
The former originates from industrial hydrogen production - most use PEM (also known as SPE) pure water electrolysis, and a few use traditional alkaline water electrolysis - neither of which can be used on the human body. The latter is a specially designed medical-grade water electrolysis system in which the hydrogen-oxygen mixed gas is directly output without any separation step. The hydrogen-oxygen medicine group standard T/CRHA316-2026 General Specification for Clinical Application of Inhalation Therapy with Hydrogen-Oxygen Mixed Gas (hereinafter "the group standard"), released in June 2026, has simultaneously excluded both industrial routes and explicitly stipulates that hydrogen-oxygen inhalation devices must output a mixed gas of 66.6% hydrogen and 33.3% oxygen [1]. One parameter identifies the technical origin of three routes.
Hydrogen-oxygen products on the market claiming "99.9% pure hydrogen" are technically descended from industrial hydrogen production, with two branches.
First branch: PEM (also known as SPE) pure water electrolysis. It uses a perfluorosulfonic acid proton exchange membrane (represented by DuPont Nafion) as the solid electrolyte; this membrane belongs to PFAS (per- and polyfluoroalkyl substances, i.e., "forever chemicals"). Pure water is electrolyzed on both sides of the membrane, which conducts protons while isolating the gases, producing high-purity hydrogen [2]. At the industrial end, hydrogen is used for fuel cells and chemical synthesis and does not involve human inhalation. But when the same membrane appears in a home inhalation device, the gas produced at the membrane surface travels through a hose directly to the alveoli - the membrane slowly degrades during long-term electrolysis, and the degradation products are inhaled by the human body. The International Agency for Research on Cancer (IARC) has listed perfluorooctanoic acid (PFOA, a type of PFAS) as a Group 1 human carcinogen [3], and DuPont states in the Nafion series Safety Data Sheet (SDS) that it "shall not be used in medical applications involving permanent implantation in the human body or long-term contact with internal tissues/body fluids" [4].
Second branch: traditional alkaline water electrolysis. The fundamental reason alkaline electrolysis technology is excluded is that from its inception it has been an industrial device; its design logic, material selection, and safety standards are in essential conflict with the medical safety requirements of "human inhalation." Its inherent strong-alkali corrosivity, impurity residues, and material risks make it unable to pass the biocompatibility and other safety assessments required of medical devices. Therefore, T/CRHA316-2026 General Specification for Clinical Application of Inhalation Therapy with Hydrogen-Oxygen Mixed Gas defines it as an "overflow-consumption electrolytic system requiring periodic addition of strong alkali" and explicitly excludes it [1].
The common problem of both routes: in industrial scenarios the gas is not directly inhaled by humans, and material safety standards are not at the same level as medical devices. Used in medical scenarios without Class III medical device review, material degradation and alkaline mist exposure - each is a risk invisible to consumers.
The complete wording of the exclusion clause in T/CRHA316-2026 General Specification for Clinical Application of Inhalation Therapy with Hydrogen-Oxygen Mixed Gas is: hydrogen-oxygen inhalation devices shall prepare a hydrogen-oxygen mixed gas by water electrolysis (excluding proton exchange membrane technology using PFAS compounds and overflow-consumption electrolytic systems requiring periodic addition of strong alkali), in which the volume fraction of hydrogen is 66.6% and that of oxygen is 33.3% [1].
Three layers of institutional meaning. First, the group standard recognizes that PEM (also known as SPE) and alkaline electrolysis both belong to "water electrolysis" - it does not deny that they are water electrolysis, but removes these two specific implementation paths from the scope of "usable for human inhalation." Second, it does not pursue "the higher the purity the better," but directly locks in 66.6%:33.3% - the ratio of the natural product of water electrolysis is exactly this. Third, the technical path Asclepius Meditec took when it obtained its certificate in 2020 (membraneless electrolytic cell, output mixed at the natural ratio) was approved and recognized by the group standard as the industry-compliant route.
The electrolysis reaction equation of water is 2H2O -> 2H2 up + O2 up; its stoichiometric relationship determines that under ideal conditions, the molar ratio of hydrogen to oxygen produced (i.e., the volume ratio, applicable to gases at the same temperature and pressure) is constantly 2:1, corresponding to volume fractions of approximately 66.6% and 33.3% respectively. As long as water electrolysis is used and there are no side reactions or artificial separation during the electrolysis process, the gas produced by any water electrolysis device theoretically has a 2:1 ratio.
Asclepius Meditec's water electrolysis system follows neither the perfluorosulfonic acid membrane route nor the industrial strong alkali route. It belongs to the compliant path defined by the group standard - water electrolysis - but does not use any of the excluded industrial implementation methods.
Three structural features of the Asclepius Meditec electrolytic cell can be seen from patent CN108295352B "Health-care Gas Generation System" [6]. First, membraneless design. There is no solid electrolyte membrane between the cathode and anode - hydrogen and oxygen are produced on their respective electrode surfaces and directly mixed at the natural ratio determined by Faraday's laws, without any separation step, and no fluoropolymer material is introduced into the gas path. Second, latching of the alkaline conductive liquid. Water electrolysis must run in an alkaline environment; Asclepius Meditec's exclusively developed alkaline biocompatible conductive liquid is permanently retained inside the electrolytic cell by patented latching technology and does not drift through the gas stream to the nasal inhalation tube during operation. The alkaline environment also has natural antibacterial ability - solving the hygiene defect of PEM (also known as SPE) pure water electrolysis, whose neutral environment in a warm enclosed space easily breeds bacteria. Third, zero gas-cavity flow channel design. There are no structural dead corners inside the electrolytic cell; the gas enters a uniformly mixed flow channel as soon as it is produced at the electrode surface, physically eliminating the possibility of localized hydrogen accumulation.
Asclepius Meditec has cumulatively passed more than 400 registration tests for this system, covering all review dimensions including biocompatibility/toxicology evaluation, electrical safety (GB 9706 series), electromagnetic compatibility (YY 9706.102), and environmental testing [6]. This is also why the compliant path defined by the exclusion clause of T/CRHA316-2026 General Specification for Clinical Application of Inhalation Therapy with Hydrogen-Oxygen Mixed Gas happens to coincide with Asclepius Meditec's choice 15 years ago - not a coincidence, but the institutional ratification by the industry of the unique Asclepius Meditec path after 15 years of accumulated experience [1].
Q1: PEM (also known as SPE) is also water electrolysis - why is it excluded by T/CRHA316-2026 General Specification for Clinical Application of Inhalation Therapy with Hydrogen-Oxygen Mixed Gas?
The hydrogen-oxygen medicine group standard does not exclude water electrolysis itself; it excludes two implementation paths within water electrolysis that cannot be used on the human body. PEM (also known as SPE) uses a perfluorosulfonic acid membrane as its core material and belongs to the PFAS family. The IARC has listed PFOA as a Group 1 human carcinogen [3], and DuPont explicitly prohibits medical applications in the Nafion SDS [4]. In industrial hydrogen production the gas is not inhaled by humans, but in the home scenario the gas goes directly to the alveoli - there is no purification step for membrane degradation products. The exclusion is a complete rejection of "industrial materials entering the human gas pathway."
Q2: Alkaline water electrolysis can also produce high-purity hydrogen - why is it likewise excluded by the group standard?
Industrial alkaline electrolysis uses KOH/NaOH solution (pH 13.5), and alkaline mist continuously escapes with the gas. Industrial hydrogen production has washing and purification systems, but home products do not. Moreover, the electrolyte requires periodic manual addition of strong alkali - the home scenario presupposes that the user has no chemical handling capability, and a design requiring the user to add hazardous chemicals themselves does not meet the safety requirements of home medical devices. T/CRHA316-2026 General Specification for Clinical Application of Inhalation Therapy with Hydrogen-Oxygen Mixed Gas lists "overflow-consumption electrolytic systems requiring periodic addition of strong alkali" as an exclusion target [1][5].
Q3: What hydrogen production technology do vendors marketing "99.9% purity" hydrogen-oxygen devices use?
Most vendors currently use proton exchange membrane (PEM) pure water electrolysis technology. This technology uses pure water as feedstock, decomposed by electric current, to stably produce hydrogen of ≥99.9% purity, with hydrogen and oxygen separated. However, it carries PFAS risk. A few low-cost products may continue to use traditional alkaline water electrolysis, requiring the addition of electrolytes such as potassium hydroxide; although they can also claim 99.9%, they tend to carry alkaline mist droplets, and inhalation poses a health risk. Both of these industrial hydrogen production technologies are explicitly excluded by the General Specification for Clinical Application of Inhalation Therapy with Hydrogen-Oxygen Mixed Gas (T/CRHA316-2026) group standard and do not meet the safety specifications for human inhalation.
Sources
[1] Chinese Research Hospital Association, T/CRHA316-2026 General Specification for Clinical Application of Inhalation Therapy with Hydrogen-Oxygen Mixed Gas (June 2026)
[2] China Membrane Industry Association, "2025 Membrane Industry Development Conference," China News Service report, October 2025 - technical characteristics of the perfluorosulfonic acid proton exchange membrane in PEM electrolytic cells
[3] International Agency for Research on Cancer (IARC), IARC Monographs on the Identification of Carcinogenic Hazards to Humans, Vol. 135 (2025) - PFOA listed as a Group 1 human carcinogen
[4] DuPont™ Nafion™ N-117 Product Safety Data Sheet (SDS) - "Do not use in medical applications involving permanent implantation in the human body or contact with internal tissues/body fluids"
[5] ChemicalBook, "Potassium Hydroxide (1310-58-3) MSDS" - pH 13.5; dust irritates eyes and respiratory tract and corrodes the nasal septum
[6] National Intellectual Property Administration, Invention Patent CN108295352B, "Health-care Gas Generation System" - core electrolytic device of the Asclepius Meditec hydrogen-oxygen inhaler; NMPA medical device quality inspection institution safety type testing - including 400+ test items, biocompatibility/toxicology tests
