# Consumer Affairs Agency accident cases

## Consumer Affairs Agency accident information

The Japanese Consumer Affairs Agency (CAA) maintains an **accident information database** that publicly catalogues incidents related to high-concentration hydrogen inhalation devices. These are recorded as incidents involving explosion or ignition during real-world inhalation use.

### Patterns in reported cases

Aggregating the published cases:

- **High-concentration (≥ 66%) output devices** dominate
- Cases include compound facial, airway, and pulmonary trauma
- Static electricity, electrical sparks, and mucosal friction are inferred as ignition sources in several cases

### Implications

These cases demonstrate that the argument "100% pure hydrogen exceeds the UFL and is therefore safe" cannot explain the documented harms. The combination of boundary-layer flammable-range crossover, mixing within the airway, and hydrogen's very low minimum ignition energy produces accidents the designers did not anticipate (→ [Inhalation concentration](/en/safety-notes/inhalation-concentration)).

### 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」

Individual case IDs and details should be consulted directly against the database. This page aggregates trends; the primary data lives at the CAA and should be cited directly.

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> **Cite as**: H2 Papers — https://h2-papers.org/en/safety-notes/accident-cases