HAZCHEM CODES

OBJECTIVE
The HAZCHEM Code system was developed by the British Fire Service for use on vehicles transporting dangerous substances in bulk to provide immediate action advice when attending an incident.
 

HAZCHEM Codes are developed and assigned to dangerous substances after careful study of their
properties and characteristics. Examples are: 3WE, 2E, 3 Y E, 1Z, 1SE, 4X

STATUTORY REQUIREMENTS
TRANSPORT
The HAZCHEM Code system has been adopted by all States in Australia for bulk dangerous substances transport, generally through adoption of the Commonwealth Government publication titled Australian Code for the Transport of Dangerous Goods by Road and Rail. In South Australia this document is given the force of law via the Dangerous Substances Act 1979 as amended.

The HAZCHEM Code for the dangerous substances carried must appear as part of the information displayed on Emergency Information Panels fitted to all vehicles transporting dangerous substances in bulk, (generally tankers - see diagram above).

STORAGE
The HAZCHEM Code system has also been adopted for use at workplaces where dangerous substances above certain quantities are kept.
Its purpose is the same as that for transport ie to provide the emergency service with immediate action advice in combating any incident involving dangerous substances.

What the HAZCHEM Code does

The HAZCHEM Code provides advice on:
(a) The type of medium to be employed in combating a dangerous substances incident where product has escaped, been spilt or is nvolved in fire.
(b) Possible violent reaction and hazard posed to the local population.
(c) Type of personal protection to be worn by persons combating the incident.

HAZCHEM Code Explained
The HAZCHEM Code consists of either two or three characters, the first being a numeral,
followed by either one or two letters.

The first character, a numeral in the range of 1 to 4, indicates the type of medium to be employed by the fire services personnel.

THE NUMERAL
Medium Selection
1 indicates the use of solid streams of water
2 indicates the use of a water fog or fine water spray
3 indicates the use of a water-based foam
4 indicates the use of a dry agent such as a dry chemical powder, eg. sodium carbonate or dry sand

The system permits a medium of a higher numeric classification to be used than that indicated, however, a medium with a lower numeric classification than that indicated should not be used.

Where the numeral 4 appears, water must not be allowed to contact the substances involved. Water may react violently with the substances or may cause poisonous or flammable vapours to be evolved.

THE FIRST LETTER
The second character in the code is a letter selected from the range P, R, S, T, W, X, Y, Z
which indicates the type of personal protection to be worn, the possibility of violent reaction, and whether the substances and the medium employed should be contained or the substances diluted. The characters are generally black on a white background.

Personal Protection
The letters P, R, W or X indicate that a full chemical protection suit and breathing apparatus should be worn.

The letters S T Y and Z may on occasion appear. These reversed characters indicate that breathing apparatus need only be worn if the substances are involved in a fire.

Frequently in text these appear in a box, ie. S T Y or Z to indicate that they are to read as a white letter on a black background.

Contain or Dilute
The letters P, R, S and T indicate dilution while W, X, Y and Z indicate containment. Both seek to reduce the hazard or prevent escalation of the incident.

'Contain' attempts to achieve this by confining the material within finite bounds and minimising environmental impact. It also allows recovery of the material where such a procedure is safe and practicable.

'Dilute' attempts the opposite and seeks to disperse the material as diffusely as possible thereby reducing environmental impact.

In cases of spillage without fire where the medium is either water jets or water fog and containment indicated, water should not be applied.

Violent Reaction
The letters P, S, S, W, Y, and Y indicate that a violent reaction may occur through such occurrences as decomposition, ignition of vapours, acceleration of combustion due to involvement of an oxidising agent or reaction with water.

THE SECOND LETTER
The third character, when appearing, is the letter E. This indicates that evacuation of persons in the neighbouring areas must be taken into consideration. Persons in the immediate area of
the incident should always be evacuated to a safer location irrespective of whether the letter E appears in the HAZCHEM Code.

Quick Interpretation of the Code
Interpretation of the HAZCHEM Codes in the field is achieved by the use of a simple scale. This scale is in four parts:

• A diagram showing the relative position of the HAWHEM Code, United Nations number of the dangerous substances and dangerous substances Class label as they appear on the Emergency Information Panels (E1Ps) fitted to bulk dangerous substances transport vehicles.
• A key to the second and third alphabetic character.
• A key to the numeric characters indicating the combating medium.
• The alphabetic characters relate to information regarding the possibility of violent reaction, indicated in the second column by the letter V in the third column the type of personal protection required and in the final column indicating whether a spillage should be contained or diluted.