Class 5 Oxidisers and Organic Peroxides

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Class 5.1 - Oxidisers

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Oxidisers cause a flammable substance to burn with a greater intensity than in air.  They can be solids, liquids or gases.  Fires involving oxidisers are difficult to extinguish as removing the fuel or attempts at smothering do not work.  The only course of action is to attempt to cool the fire down with large amounts of water.  For fire crews, this could take days to gain control.

 

Some combinations of oxidisers and fuels create explosives, for example ammonium nitrate and fuel oil create ANFO, which is used for quarry blasting.  Rather than carry ANFO by road which would be exceedingly dangerous, ANFO is carried in mobile explosive manufacturing units (MEMUs).  The ammonium nitrate and fuel oils are carried in separate compartments in the MEMU, then mixed when required to create ANFO locally, so reducing risks.

Oxidisers may have subsidiary hazards of being toxic and / or corrosive.

 

Class 5.2 – Organic peroxides

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These contain both a flammable substance and oxygen, and are often unstable substances that a liable to burn or explode when subjected to heat.  Sometimes ambient heat is sufficient, but shock can trigger reactions as well as freezing them.  Some organic peroxides, like Class 4.1 are transported under temperature control.  Overall these are treated broadly as flammable substances. 

 

As before, there are three temperatures that are important:

• Control temperature – this is the temperature the fridge is set to, the highest safe working temperature.

• Emergency temperature – if this is reached, emergency services must be called.

• SADT  – the product will burn or explode.

 

The driver must monitor the temperature of the load throughout the journey, with readouts in the cab and load compartment.  Emergency services must be contacted if the emergency temperature is reached.  The temperature can be regulated by insulation, chemical or mechanical refrigeration, however mechanical fridges must be independent of the vehicle engine, and contain no air or oxygen in the coolant.

 

The vehicles that are authorised to transport class 5.2 have uprated features, such as antifade braking and a hermetically sealed cab.

Organic peroxides are very damaging to eyes.  The minimum PPE required includes goggles, gloves and high visibility vest.  Class 5.2 may have subsidiary hazards, such as being corrosive or toxic.