Hazardous property code
HP 12 Produces toxic gases in contact with water, air or acid
Waste that releases toxic gases when in contact with water or acids.
HP 12 covers waste that releases toxic gas when it meets water or an acid. The hazard is created by contact, which makes it a property about storage and mixing as much as about the material: a load that is stable dry is not stable in every condition it might meet.
It is recorded on the consignment note as a hazard code, and it is assigned from the substances actually present in the load — which makes it a property worth settling before the waste is put anywhere it could meet them.
- Code
- HP 12
- DEFRA code
- HP_12
Sourced from DEFRA’s digital waste tracking reference data, last checked 25 July 2026.
EWC codes that commonly carry this hazard property
3 entries from the UK List of Wastes.
These are EWC entries that typically carry this hazard property, not a determination that any particular load does. Under WM3, whether a hazard property applies depends on the substances actually present and their concentrations — the producer is responsible for assessing each consignment.
- 10 03 08salt slags from secondary productionhazardousSalt slags (secondary aluminium) — release acute-toxic gas (ammonia / phosphine) on contact with water; irritant and ecotoxic.
- 10 03 09black drosses from secondary productionhazardousBlack drosses (secondary aluminium) — release acute-toxic gas on contact with water; irritant and ecotoxic.
- 10 08 08salt slag from primary and secondary productionhazardousSalt slag from other non-ferrous primary / secondary production — releases acute-toxic gas on contact with water; irritant and ecotoxic.
Related
Recording HP 12 on real paperwork?
Waste carrying HP 12 is hazardous, so it moves on a Hazardous Waste Consignment Note rather than a standard Waste Transfer Note. Our free generator produces a compliant PDF in under a minute.
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