The Risk Management Tool Box Blog

What is the Lower Explosive Limit?

Graham Marshall - Monday, September 24, 2012

Chemical storage vessels and drums that have contained flammable liquids, such as fuels, solvents, and paints can ignite or explode when exposed to “hot work” such as sparks from angle grinders, plasma cutters, welding, oxyacetylene burners and electric metal cutting saws.

This is because flammable liquids give off vapour which has an upper and lower explosive limit that works like a range.  That means that vapour can ignite and/or explode when it is below the upper explosive limit (UEL), but above the lower explosive limit (LEL).  When a flammable or combustible liquid is exposed to heat (from direct or indirect flame), the vapours given off can reach into the range between the LEL and the UEL and ignite.  This reaction can cause a fire or an explosion. Such explosions have resulted in many fatalities occurring or severe burns from the resulting fire.

As recently as July 2012, a West Australian worker was killed when a chemical drum that he was cutting with an angle grinder exploded. The drum had previously contained a flammable liquid.

In another recent case, a Queensland high school student was killed when he was using a plasma-arc torch to convert a drum into a feed bin as part of his agricultural studies. The drum had previously contained diesel oil and the oil vapours that remained in the drum exploded.

The first step towards managing the risks associated with the UEL and LEL of any potentially explosive chemicals is to obtain important safety information.

The manufacturer or supplier of the chemicals must provide this information with the chemicals they provide. The information should be provided by a Material Safety Data Sheet (MSDS) that contains information about the hazards associated with the chemical and precautions for the safe use, transport, storage and disposal.

The MSDS should include information such as the temperature that will allow vapours to rise above the LEL and subsequently ignite, and the levels of exposure that are hazardous to humans through The chemicals should also be labeled in a way that can be easily read and understood.

If a drum of chemicals arrives at the workplace without a safety label and an MSDS attached, it should be returned to the supplier.

Once emptied, the storage containers should be stored in a safe location, away from ignition sources, with their labels still attached.

The best way to prevent an injury or fatality is to ban any form of hot work on or near a vessel or drum that contained (or still contains) flammable or toxic materials.

If hot work must be undertaken, then a Permit to Work should be issued following a thorough assessment of the task to be undertaken, and ensuring all appropriate controls are in place.

It is essential that competent, experienced persons who are familiar with the hazards associated with hot works review all hot work prior to issuing approval for the work to proceed.

It is also critical that workers performing any hot-work are provided with adequate training about the hazards associated with conducting hot work on or near drums that contained flammable or toxic substances.

JSA Manual
Post has no comments.
Post a Comment

Captcha Image

Trackback Link
Post has no trackbacks.

Recent Posts


Water Corporation Occupational Overuse Syndrome UK HSE NOPSEMA Unconventional Hydrocarbons Rail Safety Hess Pollution prevention Safety Awards NOPSA Unconventional Oil Supervision Isolation Control HSE Leadership Unconventional Gas Emergency Response MSDS Save our Seafarers Campaign Nautronix Safety Culture Survey one per center LOTO Aviation Safety NORM Slips, trips and falls Road Transport Risk Management Crane lifts IFAP Psycho-social Hazards Total Oil Spill Response Marine Safety Hazard Awareness Safety Information Posters Behaviour-based Safety (BBS) Contract Risk Management Excavations Safety "one per-center's" Hierarchy of Safety Control BHP Billiton ALARP Safe Operating Procedure (SOP) Nanotechnology Procedures Health PPE Salute to Our Hero's Process Hazard Management Call Centers WMC Resources Walking Catostrophic Disaster Office Safety Bio-hazards Raspberry Ketones Scam Coal Seam Gas Safety PowerPoint Presentation US OSHA Social Responsibility Radiation Sources Workplace bullying Best bars in the oil patch Working at height Safety Moment Safety Conference Hospital Safety Drilling Thank God it's Friday Shell Toolbox talk Job Safety Analysis Santos Risk Assessment Manufacturing Woodside SPE HSE Innovation Award OSHA Fire Prevention Kinetic Energy ENI Australia Kellogg Joint Venture Energy Model of Hazards Fatigue Management Australian OSH Codes of Practice Safety Management Program Hazard Spotting TK Shipping Hot work Safety Alert Work in Confined Spaces Natural Hazard Sakhalin Energy Hazardous Substances Customer Testimonial Manual handling BP WorkSafe WA Global Harmonized System Management of Change Safety Video Situational Awareness Hydraulic Fracturing ("fracking") Incident Investigation Chevron Rosedale Abbey Mining Farm safety Risk Tool Box APPEA OHS Law Safe at Home Construction Safety WA Resources Safety CSB Newfield Railway Safety Working with explosives Electrical hazards Driving Safety Ladder Safety


Blog / Terms of Use / Site Map / Disclaimer / Risk Management Tool Box 2009. All rights reserved. Web design by Luminosity. E-Commerce by JStores.