HP3: Flammable
Waste that catches fire easily: flammable liquids with a flash point below 60°C, flammable gases, and solids that ignite through friction.
What HP3 means
HP3 covers waste that can catch fire. The legal definition has six parts: flammable liquids, pyrophoric liquids and solids that ignite within five minutes in air, flammable solids, flammable gases, waste that gives off flammable gas in contact with water, and a group of others including flammable aerosols and self-heating waste.
For liquids the test is the flash point. A liquid waste with a flash point below 60°C is HP3, and so is waste gas oil, diesel or light heating oil with a flash point above 55°C and up to 75°C.
How WM3 decides a waste is HP3
HP3 is decided by test (flash point for liquids, and the matching tests for solids and gases), or the waste is assumed to be HP3. These hazard statements point to it:
| Hazard statement | Hazard class |
|---|---|
| H220, H221 | Flammable gas |
| H222, H223 | Flammable aerosol |
| H224, H225, H226 | Flammable liquid, categories 1 to 3 |
| H228 | Flammable solid |
| H242 | Self-reactive or organic peroxide, types C to F |
| H250 | Pyrophoric liquid or solid |
| H251, H252 | Self-heating |
| H260, H261 | Gives off flammable gas with water |
The diesel band adds to the 60°C rule. A waste diesel with a flash point of 70°C is HP3, even though 70°C isn't below 60°C.
A sludge with no liquid phase is tested as a solid. A solid with a free-draining liquid, such as soil soaked in toluene, has both parts tested. WM3 also gives levels at which some water-reactive substances make a waste HP3, such as 0.2% for sodium and 0.3% for calcium carbide (WM3 page C14).
Where you're likely to meet it
- Unleaded petrol, which WM3 says is typically HP3 along with HP4, HP5, HP7, HP10, HP11 and HP14.
- Waste diesel, gas oil or light heating oil with a flash point between 55°C and 75°C.
- Waste contaminated with oil whose identity isn't known (other than diesel), where there's enough oil for it to matter.
What it changes when the waste moves
A waste needs only one hazardous property to be hazardous waste. In England and Wales it then moves on a hazardous waste consignment note in place of a waste transfer note, and the note goes with the load to the site that receives it.
On Digital Waste Tracking, the site that receives a hazardous load records its HP codes alongside the EWC code (the six-digit code from the List of Wastes that says what a waste is).
Sources
- WM3: Waste classification technical guidance (v1.2.GB): Appendix C3, pages C9 to C15; oils, pages 28 to 30
- Annex III to the Waste Framework Directive (HP1 to HP15)
- GOV.UK: Hazardous waste consignment notes
- The Digital Waste Tracking (England) Regulations 2026: the paragraphs on hazardous properties and POPs, 15 and 16
This page explains the rules. Check the waste itself against WM3 before it moves.
Get the next guide by email
We write a plain-English guide whenever the Digital Waste Tracking rules move, and these reference pages get updated with them. Leave your email and the next one comes to you.
Start on the free plan
CarrierNote is on the GOV.UK software provider list, connected to DEFRA's Digital Waste Tracking service. Receiving sites are in scope from October 2026 and carriers from October 2027, and you can be recording to DEFRA's standard from your first load, whenever you start.