Flammable liquids and ignition sources

What is an ignition source? ...and what risks do they pose on our workplaces?

An ignition source is an object that will provide enough heat energy to cause a flammable substance, being a liquid or other, to ignite and burn spontaneously.

Ignition sources can become a hazard when they are brought into close proximity to flammable substances. When this event occurs the ignition source will provide the flammable particles with enough energy to ignite, which then causes the flammable substance to burn spontaneously.

In the workplace, some ignition sources can be very easy to identify such as a naked flame, while others are not so easy to identify such as a spark produced from static electricity. However, the best way to identify an ignition source is to determine whether the object will contain enough heat to cause a flammable substance to ignite. The object might be very small, such as a spark or an ember, however these small particles can be very hot (100 C⁰+) and contain enough energy to ignite flammable substances.

There are 4 main categories of ignition sources. These include, Thermal, Electrical, Mechanical and chemical.

Some examples of Thermal ignition sources include:

Flames:

• Blow torch
• Welding Flame
• Cigarette lighter
• Stove
• Piolet Light

Hot Surfaces

• Soldering Iron
• Electric Lamp
• Cigarette but
• Hot slag
• Glowing ember

Some examples of Electrical Ignition Sources

Electrical Current

• Electric motor
• Electric Switches
• Cable Break
• Spark produced under short circuit or other fault conditions

Electrostatic Charge

• Pneumatic Conveying of Solid
• Flow of liquid in pipeline
• Rubbing of plastic or rubber
• Liquid spray generator
• Powder flow

Lightning

• Direct strike
• Induced Voltage

Stray current

• Arc Weld

Some examples of Mechanical Ignition sources

Friction heat

• Abrasive wheel
• Bearing
• Jamming of material
• Piston movement

Materials Fracture

• Cracking of metal

Some examples of Chemical ignition sources

Exothermic reactions

• Vigorous oxidising reactions
• Exothermic Polymerisation
• Exposing pyrophoric Substances (sodium metal) to air.

To prevent ignition sources from causing fires and explosions, it's important to display clear hazard identification signage in all areas where class 3 flammable liquids are stored. The Australina Standard that outlines the design requirements for safety signs is AS 1319-1994 - Safety signs for the occupational environments. This standard specifies that a sign stating "no smoking, no ignition sources within 3 meters" must be placed on all class 3 flammable liquids storage facilities. 

As you would have recognised from the examples given above, ignitions sources can come in many shapes and forms. To ensure that your workplace is adequately protected against an explosion or fire, it is recommended that you identify every ignition source in the work place and then take preventive measures to ensure that all flammable substances are stored in a safe and compliant way that will not impose any risk to your empolyees, property, plant and equipment.