Consumer Affairs Agency accident information
The Japanese Consumer Affairs Agency (CAA) maintains an accident information database that publicly catalogues incidents involving high-concentration hydrogen inhalers with device output of 67–100 vol%. The records are not limited to explosions or ruptures of the device itself: several cases involve hydrogen igniting and exploding inside the body — the nasal cavity, airway, and lungs.
Representative reported cases
The following cases are registered in the CAA public database. Consult each linked primary record for details.
- Compound facial fracture — Feb 2025, beauty salon. Case No.508163 primary record
- Internal-tissue rupture — Oct 2024, home. Case No.496203 primary record
- Bronchial perforation with major haemorrhage — Sep 2024, home. Case No.496928 primary record
- Intra-facial fracture — Jan 2024, home. Case No.478324 primary record
- Tinnitus from a blown-off device lid — Feb 2016. Case No.264488 primary record
- Hearing loss from device rupture — Jan 2015. Case No.248208 primary record
A notable pattern is that compound trauma reaching the face, airway, and lungs has occurred repeatedly even in the home environment.
A case recorded in the academic literature
A related case appears in emergency-medicine reporting: a breast-cancer patient who combined a heat-applying procedure with hydrogen inhalation developed a pulmonary contusion centred on the alveoli (combustion-type lung injury via the inhalation route), reported in 2024 (PMID 39634382). As with the CAA database cases, it occurred under device output far above the empirically validated safe concentration for the inhalation environment.
The shared condition
What these cases share is that device output concentration was far above the empirically validated safe value (10 vol%) for the inhalation environment. Output of 67–100 vol% produces documented harm that the design assumption "100% pure hydrogen exceeds the upper flammability limit (UFL) and is therefore safe" cannot explain — because boundary-layer crossover of the flammable range, dynamic mixing within the airway, and hydrogen's very low minimum ignition energy combine (→ Inhalation concentration).
Implication
Ichikawa et al. (2026) systematically reviewed these accident cases and recommend a shift to low-concentration hydrogen inhalation that keeps device output at or below the empirically validated safe value for the inhalation environment. The accumulation of cases indicates that the design philosophy of high-concentration output devices itself is now in question (→ related key papers).
Data source
- Consumer Affairs Agency Accident Information Database: https://www.jikojoho.caa.go.jp/ai-national/
- Search keywords: 「水素」, 「水素吸入」, 「水素発生」
Consult the primary data for the latest status of each case. This page prioritises links to the primary data and provides the trend and implication summary.
Cited papers
https://h2-papers.org/en/safety-notes/accident-cases