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I can smell gas – is it going to explode?

A lot of people think that if there’s a smell of gas, there’s going to be an explosion any minute. However, although a gas leak should never be ignored and you must notify your mains supplier immediately, an explosion will only take place in very specific conditions. Christophe Salvador, a gas instructor at Sibelga, explains.

Gas Explosions: The Theory

#Stage 1: How Gas Ignites

Gas may catch fire in certain conditions. Three specific factors are required:

  1. Gas at a concentration of between 5 and 15%, no more, no less
  2. Air
  3. A source of ignition: a spark or naked flame, for example. 

“If one of these three factors is missing, or if there’s too much or too little gas, nothing will happen, even if a source of ignition is present”, explains Christophe.

#Stage 2: How Gas Explodes

An explosion as such will only occur if ignition takes place in a confined space, such as a cellar, a deep trench, or a completely enclosed room. In this case, the energy released on ignition cannot escape, thus increasing the pressure in the enclosed space until an explosion takes place. All this happens very quickly. 

In Practice 

During their training at Sibelga, gas technicians are shown a strange piece of equipment – a sort of box that can reproduce ignition or a gas explosion artificially, in complete safety. 


This tool is really useful, because it shows the technicians that the theory corresponds exactly to reality and that it is neither exaggerated nor under-estimated.

What To Do

If you're in Brussels and you smell gas, don’t hesitate – call Sibelga on freephone 0800 19 400 straight away or ring 112 (fire service). 

But watch out, before ringing you should:

  1. open the doors and windows to air it out;
  2. leave the building.

Don’t imagine that airing will solve the problem all by itself! “If a considerable concentration of gas is present, ventilation may take you to within the critical 5 to 15% range”, warns Christophe. This is why it is vital not to do anything that might cause a spark or flame (such as smoking a cigarette, flicking an electric switch, lighting a candle or ringing a bell) and to wait outside the building for the Sibelga technicians to arrive.