Explosions do not commonly occur in nature, but when they do they are usually dramatic and awe inspiring - not to say also extremely dangerous if you happen to be anywhere near them.

At any time there are volcanic eruptions taking pace around the earth, however, occasionally nature will produce a huge explosion in connection with volcanic activity and these must be the largest natural explosive events which take place. Sometimes the whole side of a mountain will be blown away in these explosions, and the effects can then be seen 50 to 100 miles from the source of the explosion.

Explosions also occur as a result of impact events, and the best known of these have been meteor impacts. Mercifully these events are rare on earth. On other planets, volcanoes and impacts cause explosions with varying frequencies.

So, what is an explosion?

An explosion is a sudden increase in volume and release of energy in an extreme manner, usually with the generation of high temperatures and the release of gases.

Natural explosions are usually the result of gradually increasing pressure within a hot volcanic core which is unable to disperse due to solidified rock above it. This pressure may build up so much that once the rock above begins to disintegrate it breaks up very rapidly and the pent-up gas pressure expands equally rapidly, with very violent results.

However it is also possible for magnetic based explosions to occur. For these to happen excessive magnetic pressure within an ultra-strong magnetic source (this could be an electromagnet) can cause a magnetic explosion. Solar flares are an example of explosion common on the Sun which is heavily magnetically driven.

A high current electrical fault can create an electrical explosion by forming a high energy electrical arc which rapidly vaporizes metal and insulation material.

So far we have talked about purely physical processes and examples which we might experience in our daily lives would include the bursting of a sealed or partially-sealed container under internal pressure is often referred to as a 'mechanical explosion'. An example of that is to burst a balloon!

Explosions can also be chemical or nuclear. In chemical explosions the increase in volume and release in energy comes from a very fast gas producing chemical reaction. All bombs used in conventional warfare produce their effect by chemical explosions.

Nuclear explosions occur when radioactive materials are placed in a situation where the radioactive activity within the radioactive material can accelerate extremely emitting a huge amount of energy very quickly and often creating a similar amount of expanding gas by intensely heating and vaporizing any material in the vicinity.

The largest known explosions in the universe are supernovae, which result from stars exploding, and gamma ray bursts, which we still do not fully understand

Although all these types of explosions are interesting to consider, in real day to day life, even if we include terrorist explosions, the biggest danger to each of us, comes from much smaller explosions and in tour workplaces, and these risks come from much more prosaic causes.

Throughout Europe all citizens are protected while at work, by a set of Regulations known as the ATEX regulations, and these are defined in the ATEX Directive, which has been fully enacted since 2006. The name ATEX was coined by the French and is taken from the first two letters from the words "Atmosphere" and "Explosive".

The ATEX Regulations cover all dangerous substances which could cause an explosion and require your employer to carry out hazard identification and risk assessments whenever and wherever on his site these risks occur.

If the risk assessments show unacceptable explosion or related dangers where the risk remains after ameliorative measures have been considered and where necessary implemented, then either alternative methods must be sought to reduce the residual risk to an acceptable level, or ATEX zones must be demarcated, and training be carried out for all staff, and provided by the Employer.

In factories solvents which evaporate may combust, and dusts of various types may also cause explosions, if there is an ignition source present.

Boiling liquid and expanding vapour explosions are also a type of explosion that can occur when a vessel containing a pressurized liquid is ruptured, such as a boiler causing a rapid increase in volume as the liquid evaporates.

All these risks must be considered within and ATEX Risk Assessment, and these and the work needed, and training needed, to provide for a safe working environment must all be documented and agreed amongst senior staff. The place to keep all this information is within an Explosion Protection Document, and this once produced needs to be kept current by regular revision by the Employer.

Further information on the ATEX Directive and the Dangerous Substances and Explosive Atmosphere Regulations is availabe at the UK ATEX and DSEAR web site.

Continue also to the ATEX and DSEAR Directory.