Toxic substances are chemicals or mixtures of chemicals that can damage organisms. The ADG Code, which is a code of practice that outlines the requirements for transporting dangerous goods, provides us with a definition of toxic substances. Their definition for Division 6.1 Toxic Substances is outlined below:
'Division 6.1 - Toxic Substances: These are substances liable either to cause death or serious injury or harm to human health if swallowed or inhaled or by skin contact.'
There are three main ways in which toxic substances can enter your body and cause harm to your health. These include:
- Skin absorption
Of these three routes of exposure, inhalation is the most common form. This form of exposure occurs when airborne toxic particles enter your lungs while breathing. Ingestion is the second most common form of exposure. Ingestion of toxic substances mostly occurs from unhygienic practices such as eating and drink with hands that have not been washed after handling toxic material. Skin absorption is the least common form of exposure and it occurs when toxic substances are absorbed through your skin.
There are a number of toxic substances that are used in the workplace on a regular basis. Some of these toxic substances include; methylene chloride, isopropyl alcohol and hydrogen peroxide.
To protect the people in your workplace from the many risks associated with toxic substances, it is very important to store them in a safe and compliant storage facility. The Australian Standard AS NZS 4452-1997 - The storage and handling of toxic substances outlines the requirements for the safe storage of toxic substances. This standard outlines different requirements for indoor storage and outdoor storage facilities. Below we will discuss the requirements for indoor toxic substance storage cabinets.
To ensure that toxic substances pose the least amount of risk to your organisation, it’s important that you keep them in a safe and compliant storage facility. Section 18.104.22.168 of AS NZS 4452-1997 sets out the construction and design requirement for safe indoor toxic storage cabinets. These requirements are outlined below:
- The roof, floor, door and walls of the cabinet must have a double walled sheet steel construction. The sheet steel must be at least 0.75mm thick. Their must be a space of at least 40mm between the walls of the cabinet. This space may be an airspace or filled with a non-combustible material.
- The doors of the cabinet shall be self-closing and close-fitting.
- The doors of toxic substance storage cabinets shall be lockable.
- The bottom of the cabinet shall form a liquid-tight spill containment sump. This sump must be at least 150mm deep and capable of containing at least 25% of the maximum storage capacity of the cabinet.
- Any shelves inside the cabinet shall be perforated to allow for free air-flow within the cabinet.
- Any materials that form the structural integrity of the cabinet must not melt at temperatures of at least 850 degrees celsius. Seals and gaskets are an exception to this requirement.
The Australian Standard AS NZS 4452-1997 does not make ventilation of toxic storage cabinets a mandatory requirement, but it gives you the provision to do so if required. If the toxic substance being stored is listed in the workplace exposure standards, and the concentration of the airborne contaminants from the toxic substances exceeds the maximum limit outlined in the workplace exposure standards, ventilation will be required. Inhalation is the most common form of exposure to toxic substance and it’s a good practice to ventilate indoor toxic substance storage cabinets to minimise the risk of exposure to people in the workplace.
If you carry out a dangerous goods risk assessment and you determine that ventilation is required for your toxic storage cabinets, it’s important to ensure that the ventilation system that you install on your cabinets meets the specific requirements outlined in AS NZS 4452-1997. These requirements are outlined below:
- Any vent opening on the cabinet shall be designed in such a way that it does not compromise the structural integrity of the cabinet.
- The ventilation system on the cabinet shall be capable of keeping the ambient concentration of airborne toxic substances in the breathing zone of any person using the cabinet at the lowest limit possible.
- Where a toxic storage cabinet has the provision to be connected to an external ventilation system:
- The vent opening shall be provided with the means of permanent closure when venting is not required.
- The information supplied with the cabinet shall include instructions on how to install and operate the venting system.
- The cabinet vent shall be designed in such a way that the surrounding work areas are not contaminated by emissions.
- The ventilation system shall also be designed by an appropriately qualified engineer.
Maximum storage quantities
To reduce the risk or exposure, whether this be by inhalation, ingestion or skin contact, it’s important to keep the quantity of toxic substances stored indoors to the absolute minimum. AS NZS 4452-1997 sets out the maximum storage quantities for indoors. This standard states:
- The maximum quantity of toxic substances kept in a single cabinet shall not exceed 250 L or Kg.
- Of this 250 L or Kg that is stored in a single cabinet, no more than 50 Kg or L shall be of packing group II and no more than 25 L or Kg shall be of packing group I.
To ensure that toxic storage cabinets poses the least amount of risk upon the people, property and environment of your workplace, it’s important to position your cabinet in a safe location. The positioning requirements for toxic storage cabinets is outlined below:
- A cabinet storing toxic substances shall not be located in relation to stairways and exits in such a way that it impedes the escape of people in the event of a fire.
- A toxic storage cabinet must always be located near a provision for the washing of hands.
- Irrespective of the occupancy of the building, no more than one toxic storage cabinet shall be located in each 100 square meters of floor space. Each toxic storage cabinet must be separated by at least 3 meters.
To ensure that everyone in your workplace, including visitors and workers, are aware of the hazardous toxic substances that are stored in your workplace, each toxic storage cabinet must display the relevant safety signage. The safety signage requirements for toxic storage cabinets is outlined in Worksafe Australia’s Guidance Note for Placarding Stores for Dangerous Goods and Specified Hazardous Substances [NOHSC: 3009(1990)]. The only exception is when the requirements of Worksafe’s guidance note conflicts with the requirements of the relevant regulatory authority for your State or Region. In this situation the requirements of the state regulatory authority will prevail. In all instances, the safety signage and lettering shall be of contrasting colour to the colour of the toxic storage cabinet. The required safety signage for toxic storage cabinets according to Worksafe’s guidance note is shown below:
Dangerous Goods Division 6.1 Safety Sign
Types of substances stored
Toxic storage cabinets should only be used for the storage of toxic substances. Toxic substance is incompatible with a number of other dangerous goods. When incompatible dangerous goods mix they cause violent chemical reactions. Some classes of dangerous goods that are incompatible with toxic substances include:
As toxic substances can cause a lot of harm to the people, property and environment of your organisation, it’s very important that you store toxic substances in a compliant toxic storage cabinet. For maximum safety, it’s also important that you do your research on the compatibility of toxic substances with other classes of dangerous goods so that you can segregate them in a compliant manner. For more information on how to safely segregate toxic substances from other incompatible classes of dangerous goods, download our free dangerous goods segregation chart by clicking on the image below.