Definition
Modality confusion is the single most common source of misleading comparisons. Millilitres per minute of gas, parts per million dissolved in water and bath concentration are three different scales.
Establish the modality first, then compare inside it.
Modality relevance
This site treats inhalation and bathing as its two device modalities, with hydrogen-rich water covered as a related format.
Purity relevance
Purity language attaches to the machine and its cell, and applies across all modalities.
Science relevance
Because studies specify a delivery route, evidence should always be read against the modality it tested.