Gas chromatography (GC) will be considered the primary method for measuring molecular hydrogen.  GC should be the most reliable method for specialists in chemical analyses. In brief, this method requires the transfer of H₂ from the aqueous phase to the gas phase using a tightly closed vessel, where hydrogen concentration can be measured by GC.  The standard operating procedures (SOP) for measurement by GC will soon be determined by IHSA to mitigate systematic errors.

IHSA will also adopt a secondary method using an electrode that is specific to hydrogen. Several electrodes are currently available commercially; however, each has merits and shortcomings. Thus, one electrode will be carefully selected for the measurement, and the standard operating procedures (SOP) will be established by IHSA. While there may be other suitable options for general consumer use, these will not be considered for use in IHSA performance certifications. For example, IHSA may recommend different brands of electrodes, sensors, use of approved redox titration reagents, etc. However, methods that depend on the measurement of the oxidation-reduction potential (ORP) to estimate hydrogen in water, which incorporate electrodes which are not specific to hydrogen, are discouraged. Although a negative ORP is one of the characteristics of hydrogen water, ORP itself does not show the hydrogen concentration. Thus, technologies which rely upon measurement of ORP should not be used as a method to measure the hydrogen concentration.

The unit of measure for hydrogen concentration

IHSA will use the unit of milligrams per liter (mg/L) and not parts per million/billion (ppm/ppb) when discussing the concentration of hydrogen in water. This will help reduce the confusion from the multiple uses. For example, ppm can be used in chemistry as a mass (wt/wt), a mole (mol/mol), a volume (vol/vol), or weight/volume (wt/vol) fraction. Similarly, in physics, ppm can be used as proportional phenomena of length (α = 1.2 ppm/°C), or uncertainty in measurements (accuracy =1 ppm), or the chemical shift in spectroscopy (2 ppm). Additionally, the billion in ppb may represent different values to different countries (10⁹ or 10¹²). Moreover, ppm is not recognized by the International System of Units (SI) and thus not an SI-compliant expression, and the ISO recommends against their use. Thus, for the IHSA standards and certifications, milligram (mg) and milligram per liter (mg/L) are adopted as the units of measure for dose and concentration of hydrogen, respectively.