How to Read a Hazchem Code

A Hazchem code is a number from 1 to 4, a letter, and sometimes an E (ADG Code 7.9 Appendix C). The number says what to put on a fire, from coarse water spray (1) to a dry agent (4); the letter covers protective gear and run-off; E means the public may be at risk.

Ordering a HAZCHEM sign? Here is how to read the code you will print. A Hazchem code is the short code on a dangerous goods panel, like 4WE, that tells a fire crew in seconds how to fight a fire or handle a spill: what to spray, what to wear, whether the run-off can go down the drain, and whether the public is at risk. Each character has a fixed meaning, so once you know the key you can read any code.

The code goes on a bulk storage sign or an emergency information panel. The sign at the gate that just says HAZCHEM is the outer warning placard, which carries no code.

Where you see one

On the emergency information panel of a tank vehicle, bulk container or portable tank, where the Australian Dangerous Goods Code requires it, and on bulk storage placards at a workplace. The code is also called the Emergency Action Code.

The first character: what to put on it

• 1 coarse water spray
• 2 fine water spray
• 3 foam (normal, not alcohol resistant)
• 4 dry agent: water must not touch the substance

A higher number can always be used instead, never a lower one. In the official list a bullet before a 2 or a 3 means alcohol resistant foam is preferred. The bullet does not have to be shown on the panel.

The letter: what to wear, how it reacts, where the run-off goes

The second character is one of eight letters. Each answers three questions at once.

Dilute means that where people are at immediate risk, a spill may be washed to drain with large amounts of water. Contain means spills and fire water must be kept out of drains and waterways. Can react violently means the substance may react violently or even explosively, for example a flammable vapour cloud igniting or a violent reaction with water.

The E: a risk to the public

An E after the letter means the danger may reach beyond the incident itself. People nearby may be told to stay indoors with doors and windows shut, and emergency services consider whether an evacuation is needed. No E means the code is just two characters.

Reading a code

Take 4WE: 4 means use a dry agent and keep water off it, W means a liquid-tight chemical suit with breathing apparatus, a risk of violent reaction, and contain the spill, and E means warn the public.

Finding the code for your chemical

Hazchem codes are listed by UN number in Appendix C of the Australian Dangerous Goods Code, published by the National Transport Commission:

Source: ADG Code Appendix C: Emergency Action (Hazchem) Codes

. A substance can have more than one code, chosen by its packing group. Several dangerous goods carried together get one combined code, worked out with the method in the same appendix.

Signs that carry a Hazchem code

Each of these is printed to order with the code you give us.

Common questions

What does the number in a Hazchem code mean?

It tells firefighters what to put on a fire or spill: 1 is coarse water spray, 2 is fine water spray, 3 is foam and 4 is a dry agent, where water must not touch the substance. A higher number can be used, never a lower one.

What does the E at the end mean?

There may be a danger to the public beyond the incident itself. People nearby may be told to stay indoors with doors and windows shut, and evacuation may be considered.

Where do I find the Hazchem code for my chemical?

In Appendix C of the Australian Dangerous Goods Code, published by the National Transport Commission, listed by UN number.

Figures on this page were checked against the linked sources on 2026-11-02.