The Dangerous Combustibility of Dust
Aftermath of 2008 explosion at Imperial Sugar in Port Wentworth, Georgia, US
Dust is everywhere. It’s in our homes, our cars and our places of work. There’s no escaping dust and because of this, it’s very easy to ignore the potential dangers that it holds. We’re not talking about asthma or allergies, we’re talking about fires and explosions.
Some places are very dusty, not just with ‘everyday’ dust, but dust that is produced through manufacturing processes or the environment. This dust can be sawdust from a wood processing plant, flour/malt dust in a mill, or sugar dust used in food manufacturing. In small controlled quantities, they’re as harmless as you would expect. However, in agitated environments and large quantities, the dust becomes suspended in the air, like when pouring powdered sugar, sawing lumber or milling grain.
When this organic (and therefore flammable) material is dispersed into the air it becomes a dangerous mix of fuel and oxygen, simply waiting for a heat source to complete the fire triangle. This is how dust explosions occur.
You may not realise but heat sources are everywhere. They are in electronic switches when they are turned on, in motors as they spin and in light fittings, to name a few. It doesn’t take much to cause an ignition. Flammable dust should be thought of as the same as flammable gas.
Ignition of a single dust particle can be caused by even the smallest of sparks or heat sources. This causes the dust particle to combust, using the available oxygen around it. This combustion then causes adjacent dust particles to also ignite, and the rapid chain reaction occurs.
The combustion is rapid and forceful and when in the usually confined spaces of factories and workshops, the results are explosive. This is why when talking about dust explosions the Fire Triangle is expanded to a Fire Pentagon – Fuel, Oxygen, Heat, Dispersion and Confinement.
Studies in 2011 estimated that there are around 2000 dust explosions occurring in factories and refineries in Europe each year and approximately 50 of these occur in the UK alone. So, what are the steps for minimising the fire risk of a dust explosion?
In the UK, any companies that are at risk of dust explosions must adhere to the Dangerous Substances and Explosive Atmosphere Regulations 2002 (DSEAR). The regulation outlines a requirement for businesses to find out which dangerous substances are present in the workplace and establish the explosion risks that are present. The regulations also require businesses to put control measures in place to remove these risks where possible, otherwise reduce and control them.
This can be anything from non-spark switches and electronics to increasing the humidity of the environment. If you feel that that is a danger to yourself or other co-workers through dust build up and potential ignition, it’s important that you speak to the responsible person immediately. Dangerous dust and environments are a risk that should be properly identified during a Fire Risk Assessment.
An unconfined dust explosion - Dust fired into the air with compressed air and ignited with a road flare - Courtesy of Mythbusters "Creamer Cannon"