What happened

A quarry worker received serious burns when he was engulfed in flames from burning diesel.

Investigation

A Department of Labour investigation found the accident occurred when a workmate of the victim added diesel to a smouldering fire in a drum at a quarry in Central Otago.

This is the second accident in 13 months where adding diesel to a fire in a drum has lead to serious burns.

To keep warm during very cold conditions wood fuel fire was started in a cut down drum (see figure 1).

At lunch time the fire had died down and an employee decided to relight the fire, using diesel. Diesel fuel was poured from the plastic container onto the fire. Two of his workmates were seated near the drum, as this was the area where they had decided to eat their lunch.

As the diesel was poured onto the smouldering fire the fuel ignited and flashed into a fireball. The flames engulfed the employee seated on the large rock opposite the fire shown in the photo.

Click image for larger copy
Figure 1: Fire drum and rocks used for seating.

The resulting fireball set fire to the employee's clothes. The employee was wearing overalls made mainly of nylon fibres, these melted as they caught fire. The melting fibres made the fire more difficult to extinguish, adding significantly to the burns received by the worker.

Diesel fuel will give off sufficient vapour to form an ignitable mixture with air when the temperature of the fuel reaches 52 to 80°C.

Adding diesel fuel to a smouldering fire has the possibility of forming a large flammable atmosphere around that fire, as the heat contained in the fire will vaporize the liquid at these warm temperatures.

If the fire then ignites, this flame will ignite the vapour, which is explosive at low concentrations (explosives limits of diesel, volume in air 0.6 to 6.5% and ignition temperature (254 to 285°C).

Comments and preventative action

Diesel and other flammable liquids should not be used to light fires and especially not on any existing fires.

If people are required to work in cold environments the hazards need to be identified and controlled. Strict controls need to be place based on the risk assessment of lighting fires. Nylon/polyester overalls should not be worn where there is a risk of clothing catching fire. The Department of Labour Guidelines for Work in Extremes of Temperature provides guidance for this hazard. See web site www.dol.govt.nz.

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Issued by the Department of Labour, New Zealand
http://www.osh.dol.govt.nz

No. 19 - September 2006