Flammable solids, as the name suggests, are dangerous goods which can cause a fire or spontaneously combust. As volatile chemicals, Class 4.1 Flammable Solids require careful handling and storage to minimise human harm and property damage. In Australia, the requirements for storage of each class of dangerous good is detailed in the relevant Standard. In this post, we’ll be referencing the Australian Standard AS NZS 5026:2012 to highlight some key considerations that you must make when storing flammable solids in your workplace. 

Defining Flammable Solids 

The Australian Dangerous Goods (ADG) Code is a comprehensive guide that provides a definition for each class of dangerous goods.  

The ADG Code explains that Class 4 Dangerous Goods are divided into 3 divisions:  

  • Class 4.1 Flammable Solid 
  • Class 4.2 Spontaneously Combustible 
  • Class 4.3 Dangerous When Wet 

The Code explains that Division 4.1 Flammable Solids are readily combustible solids and solids that may cause a fire through friction. The ADG Code gives us this explanation of the properties associated with this particular dangerous goods division: 

Solids which, under conditions encountered in transport, are readily combustible or may cause or contribute to fire through friction; self-reactive substances which are liable to undergo a strongly exothermic reaction; solid desensitized explosives which may explode if not diluted sufficiently;  

What are the Risks? 

As the Code highlights in this definition, flammable solids are chemicals which include self reactive substances, polymerizing substances and solid desensitized explosives. 

Flammable solids are chemicals which have the ability to: 

  • Combust 
  • Self-react 
  • Produce an exothermic reaction 
  • Explode 
  • Cause a fire 
  • Contribute to a fire 

Another safety issue related to the storage and handling of flammable solids is the flammable gases that can be emitted from the product. Flammable gases are denser than air, and can quickly accumulate in storage spaces, rooms and low-lying areas around the workplace. When the gases travel near an ignition source, they will ignite — sparking a fire. 

Flammable substance fire at a workplace

Flammable solids can cause fires and explosions if they're not handled and stored in the right way.

Therefore, careful management of these substances is required to control these serious flammable solid risks. 

In the next section of our blog, we’ll be detailing some key controls that you can easily implement in your own workplace to ensure your flammable solids stores are safe and compliant with Australian Standards. 

Flammable Solids and Ignition Sources 

Flammable solids are dangerous goods which have flammable properties. Similar to other flammable dangerous goods classes, including liquids and gases, flammable solids must be isolated from ignition sources to prevent fire and explosion hazards. 

As we’ve explained, flammable solids can spontaneously combust — they can spark a fire. Their flammable gases can quickly travel through workplaces, accumulating in low-lying areas of your business. 

If the gases or the chemicals are exposed to excessive heat or ignition sources, fires and explosions can occur.  

Therefore, you must ensure that all ignition sources are identified and isolated from your flammable solid handling and storage areas. 

This means that you must display the correct dangerous goods diamond on your cabinet or store, as well as the No Smoking, No Ignition Sources Within 3 Metres sign. 

If your staff are untrained in flammable solids safety, they may not be able to accurately identify the ignition sources in your business. Ignition sources may be items which are static (power points) or items which can be physically brought into the work area by workers or contracts (lighters). 

Some common types of ignition sources may include: 

  • Heat – such as light bulbs, exothermic chemical reactions, ovens, vehicle engines 
  • Sparks –  including static electricity, mobile phones, electric motors, welding arcs 
  • Flame – examples include lighters, torchers, gas heaters 

Furthermore, the Australian Standard for flammable solids, AS NZS 5026:2012The storage and handling of Class 4 dangerous goods, explains the rules for the isolation of ignition sources when storing them in a Class 4 storage cabinet: 

5.7.7 Exclusion of ignition sources  

There shall be no ignition sources within the cabinet.  

Ignition sources shall be excluded from the area outside the cabinet to a distance of 3 m, measured laterally, and from floor level to a height of 1 m above any opening into the cabinet, including the door opening. 

ignition source welder at work

Train staff and contractors to correctly identify and isolate ignition sources, especially those that may be unintentionally brought into a flammable solids handling or storage area.

Adequate Ventilation of Handling and Storage Areas 

Due to the emission of flammable gases from your flammable solids, adequate ventilation is required in all handling and storage work areas. 

As we’ve mentioned earlier in this blog, if flammable solids aren’t properly contained, the heavy gases can escape into the workplace and accumulate in low lying places. 

Therefore, due to the risk of ignition, your flammable solids must also be stored and handled in a well-ventilated area to ensure that gases don’t build up in your workplace or stores.  

The Australian Standard that relates to flammable solids offers further advice on ventilation requirements. AS NZS 5026:2012The storage and handling of Class 4 dangerous goods includes specifics about package stores and their construction.

Within Section 5.5, the Standard explains that: 

Adequate natural or mechanical ventilation shall be provided for all storage and handling areas (see Clause 9.2.5).  

Where mechanical ventilation is required, it shall comply with AS 1668.2/NZS 4303.

Referencing Clause 9.2.5, the Standard further explains that: 

Adequate ventilation is dependent on the nature of the substance being kept and the circumstances of its use.  

It's important to remember that Class 4 dangerous goods include Division 4.1 flammable solids, self-reactive substances and solid desensitized explosives. While the Standard explains in Section 6.4 that solid desensitized explosives and nitrocellulose require ventilation, we recommend referring to your SDS and conducting a risk assessment to determine your product’s ventilation requirements. 

Segregating Flammable Solids from Other Dangerous Goods 

When storing any class of dangerous goods, you must understand and acknowledge the rules for chemical segregation. 

Flammable solids, just like most classes of dangerous goods, require careful segregation to keep them safe in the working environment. 

The Standard explains the requirements for segregation of Division 4.1 solids. 


5.7.1 General This Clause (Clause 4.7) applies to the storage of Class 4 dangerous goods in cabinets.  

Class 4 dangerous goods that are incompatible or react dangerously with each other shall not be kept in the same cabinet. 

Flammable solids are incompatible with many other types of dangerous goods. They may also be incompatible with dangerous goods within the same class. 

SC205H Class 4.1 storage cabinet 250 litres

Division 4.1 solids must be segregated from: 

  • Division 2.1 Flammable Gas – by at least 5 metres 
  • Class 3 Flammable Liquids – by at least 3 metres 
  • Division 4.2 Spontaneously Combustible – by at least 3 metres 
  • Division 4.3 Dangerous When Wet - by at least 5 metres 
  • Division 5.1 Oxidising Agents – by at least 5 metres 
  • Division 5.2 Organic Peroxides – by at least 5 metres 
  • Class 6 Toxic Substances – by at least 3 metres 

You must also check your product’s SDS to determine if your flammable solids are able to be kept near Division 2.2 Non-Flammable, Non-Toxic Gas stores nor any Class 8 Corrosive Substances. 

Division 4.1 dangerous goods, therefore, must only be stored with other Division 4.1 Flammable Solids. 

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If your workplace does not have the space required to practice these segregation rules, you must choose a Class 4 storage cabinet for your flammable solids. These cabinets provide adequate protection for your chemicals, as well as dangerous goods segregation, so multiple classes of dangerous goods may be safely stored in the same work area. 

Maintaining Class 4.1 Signage 

We often speak about the importance of maintaining your dangerous goods diamond and hazard signage. The signage is not only a requirement of the Australian Standards, it’s also vital for the safety and awareness of staff, supervisors and contractors. 

If flammable solids are kept in a Class 4 storage cabinet, it must be marked with the following signage: 

5.7.4 Cabinet marking  

Each cabinet shall be marked with—  

(a) the name and address of the manufacturer or, for imported cabinets, the distributor within Australia/New Zealand;  

(b) the maximum storage capacity;  

(c) the relevant dangerous goods division label with sides of at least 250 mm nominal length; and  

(d) a sign bearing the words ‘NO SMOKING, NO IGNITION SOURCES WITHIN 3 m’ in lettering at least 50 mm high.  

Class 4.1 – Flammable Solids

No smoking no ignition source within 3 meters

REMEMBER: All signs and markings shall be clearly visible when the cabinet doors are closed. You should also ensure that signs aren’t vandalised, aged or in general disrepair, as this can put you at risk of non-compliance. Create a regular cabinet inspection and maintenance program, to ensure that your flammable solids storage cabinets are being used and maintained in a safe and compliant way. 

Maximum Quantities Kept 

Flammable solids are subject to maximum quantity restrictions to protect staff, property and the surrounding community from the fire and explosion risks associated with these chemicals. 

When keeping flammable solids in indoor chemical storage cabinets, the Standard explains that: 

5.7.2 Maximum quantities to be kept  

The maximum capacity of a cabinet in which Class 4 dangerous goods shall not exceed 250 kg or L. No cabinet shall hold more than 25 kg or litres of Category A, 50 kg or L of Category B or 100 kg or L of Category C.  

NOTE: Units of kilograms (kg) apply to solids and units of litres (L) to liquids. 

You should select a Class 4 storage cabinet that meets your chemical capacity requirements and allows staff to fill the cabinet without the risk of overload. Staff should be trained to identify the maximum capacity for each cabinet and follow safe stacking and loading procedures to reduce the likelihood of the containers or drums toppling during storage. 

IMPORTANT: Due to the diversity of chemical properties and reactivity of Class 4 substances, it’s not possible for the Standard to provide detailed requirements for every situation involving storage and handling of any substance within the class. Therefore, workplaces must perform a hazard identification and risk assessment specific to the substances and activities at the workplace. 

How are you Storing Flammable Solids in your Workplace? 

Thanks for reading our post about the key considerations for flammable solids storage. As we’ve highlighted, keeping your chemicals stored safely includes consideration for the exclusion of ignition sources, as well as practicing effective dangerous goods segregation and the monitoring and control of flammable gases and vapours.

To find out more about improving safety in your organisation, you can download our free guide. Our eBook details the risks associated with the 9 classes of dangerous goods, as well as key controls you can implement to reduce the likelihood of fire, explosion and chemical reactions. Grab your own copy right now, by clicking on the link below. 

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