Ep.30: Spontaneously Combustible Substances: The Fire Risk You Didn't See Coming

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Hello and welcome to Chemical Safety at Work, the podcast that helps you better understand dangerous goods and the steps you can take to keep your workplace safe and compliant.
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I'm your host, patrick G, and today we're talking about a particularly dangerous and often misunderstood group of chemicals spontaneously combustible substances.
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Now, if you're working with materials like white phosphorus or aluminium alkyls, this episode is especially important.
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These substances can actually ignite on their own just from being exposed to air.
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Let's dive into what makes these chemicals so dangerous, how they're classified and how to safely store and handle them in your workplace.
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So what exactly is a spontaneously combustible substance?
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As the name suggests, these chemicals can self-ignite when they come into contact with oxygen, sometimes in just a matter of minutes.
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These substances fall under class 4.2 of the Australian Dangerous Goods Code, that's the division specifically for substances liable to spontaneous combustion.
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Class 4 is split into three divisions Division 4.1, flammable solids, division 4.2, spontaneously combustible substances, and Division 4.3, dangerous when wet.
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Today we've focused on Division 4.2, and there are two key categories here Pyrophoric substances, which ignite within 5 minutes of air exposure, and self-heating substances, which catch fire slowly over hours or days, especially in large quantities.
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These substances can be incredibly dangerous if not handled correctly.
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We're talking about human harm from exposure, fire and explosion risks, toxic gases released during a fire, contamination of air, land and water, reactions with incompatible chemicals and, of course, major property damage.
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And because of these risks, class 4.2 substances are assigned a packing group which tells you how dangerous the chemical is.
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There are three levels Packing group 1, high danger.
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Packing group 2, medium danger and packing group three, low danger.
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For example, pyrophoric solids and liquids are packing group one.
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Meanwhile, self-heating organic substances might fall into packing group two or three, depending on the level of risk.
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You'll find the packing group in the safety data sheet, so always check the STDS before working with any new substance.
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Storage is absolutely critical when it comes to spontaneously combustible substances.
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The Australian standard ANNZS 5026 outlines what's required when storing class 4 dangerous goods.
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Let's run through the main options goods.
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Let's run through the main options A freestanding, roofed chemical store, a room attached to an external wall, a specially designed area inside a building with a fire resistant wall or, where appropriate, an open air storage facility and, of course, a compliant, fire resistant chemical storage cabinet.
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If you're using a cabinet and many workplaces do it needs to meet very specific requirements.
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It must be made from double walled steel.
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The internal space within the walls needs an air gap of at least 40 millimeters.
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The bottom must contain any leaks, at least 150mm deep and liquid.
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Tight Shelves should be perforated to allow air movement.
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Doors must be self-closing and held shut by a friction or magnetic mechanism that'll release under pressure and, importantly, components must not melt under 850 degrees Celsius.
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All of this is designed to give you time to react if something goes wrong and to prevent a small issue from becoming a disaster.
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Storage cabinets must also include clear signage.
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Here's what you'll need A class 4.2, spontaneously combustible label at leastimetres long, no smoking, no ignition sources within three millimetres.
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In letters, at least 50 millimetres high, the cabinet's maximum capacity and the name and address of the manufacturer.
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Now let's talk ventilation.
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If there's any chance of your stored substances releasing toxic or flammable vapours, mechanical ventilation is a must.
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That means ducting designed to prevent back pressure, and it must direct fumes away from ignition sources and anywhere where people might gather.
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Speaking of ignition, this one's simple but essential there must be no ignition sources within three meters of your class 4.2 cabinet.
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That includes sparks from equipment, hot surfaces, static discharge, even someone lighting a cigarette on their break.
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Make sure your team understands this and make sure they've been trained to recognize these risks.
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All of this storage signage exclusions.
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It only works if your people understand what they're dealing with.
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All staff and contractors must be trained in how to safely store and handle class 4 substances and how to identify and eliminate hazards.
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Don't forget to carry out a risk assessment of your site.
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That's your roadmap for making sure every hazard is accounted for and controlled.
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So to wrap it up, spontaneously, combustible substances class 4.2, are extremely dangerous, but with the right systems in place, they can be stored and handled safely.
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Always check your SDS, choose the correct storage solution, mark your cabinets clearly, train your team and keep ignition sources well away.
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Thanks for tuning into Chemical Safety at Work.
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We'd love to hear from all of our listeners, so send us a message and let us know if there are any topics you'd like us to do a deep dive on.
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Until next time, stay safe, stay compliant and always respect the risk.
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Until next time, stay safe, stay compliant and always respect the risk.
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Until next time, stay safe, stay compliant and always respect the risk.
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Until next time, stay safe, stay compliant and always respect the risk.