Controlled Zones

What is a Control Zone?

The HSNO Act introduces the concepts of Controlled Zones and separation. These concepts are applied to class 2 (flammable gases like LPG) and 3.1 (flammable liquids like petrol and diesel) hazardous substances in the Hazardous Substances (Dangerous Goods and Scheduled Toxic Substances) Transfer Notice 2004 , Schedule 10.

This is a very technical subject and it advisable to use a suitably qualified person to create any plans you need. Talk to your Test Certifier to see if you need a plan.

The technical definition of a €˜Controlled Zone' is:

An area abutting a hazardous substance location that is regulated so that:

  1. within the zone, the adverse effects of a hazardous substance are reduced or prevented; and
  2. beyond the zone, members of the public are provided with reasonable protection from those adverse effects.

In this definition, hazardous substance location means the physical position (i.e. the "foot print") where the hazardous substance is located (e.g. the tank), as opposed to the broader interpretation used when referring to a location test certificate.

The technical definition of a Hazardous Atmosphere Zone from AS/NZS 2430.3.1:2004 is:

An area (three dimensional) in which an explosive atmosphere is present, or may be expected to be present, in quantities such as to require special precautions for the construction, installation and use of potential ignition sources.

Examples of potential ignition sources are electrical equipment, naked flames, sparks from grinding and welding operations, hot surfaces.

These are some other terms that you need to know about:

Area of High Intensity Land Use [HILU]
Areas where persons are frequently present, such as buildings.
Area of Low Intensity Land Use [LILU]
Areas where persons are present only occasionally, such as public parks.

How do you apply Controlled Zones?

The concept of a Controlled Zone is separate from the concept of a Hazardous Atmosphere Zone. Both have different requirements.

At a site where a Controlled Zone is required, it is necessary to meet the HILU separation requirements to areas of high intensity land use and also the LILU separation distance to areas of low intensity land use. Non authorized personnel are excluded from the controlled zone unless the site is a retail site with appropriate warning signs.

Where a hazardous substance location is established and the observance of separation is applicable, it is necessary to overlay the controlled zone contours (showing the full extent of the separation to be observed) over the actual site features.

What if my Controlled Zone extends over my boundary?

In the event that the contour extends over the legal boundary of the property or extends over an area of HILU or LILU, there is a potential non-compliance There is provision in clause 32 of Schedule 10 for extending the controlled zone over the boundary of the property.

If the required separation distances cannot be achieved, there is provision in clauses 33 and 35 of this Schedule 10 to enable reduced separation to be applied, provided that certain criteria are met and/or certain measures applied. This may enable the non compliance to be alleviated.

One of these measures is an intervening wall placed between the hazardous substance location and the HILU/LILU as depicted below.

What might a plan look like?

Diagram of Controlled Zone

(Image links to larger version)

Further information