Rank: Forum user 
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Dear All,
I found different definitions for Explosives & Flammable. For e.g., Explosives is defined in relation with dinitrobenze (as mentioned below):
//Explosive
Substances and preparations which may explode under the effect of flame or which are more sensitive to shocks or friction than dinitrobenzene.
Another one says: It is "A chemical substance or mixture in which fuel and oxidising agent are combined".
Flammable
Liquid substances and preparations having a flash point equal to or greater than 21ºC and less than or equal to 55ºC.
Definition II: Highly Flammable Liquid - A (liquid) substance which has a flash point of less than 32°C.
Any UK directive where I shall get the standard definitions?
Regards,
Prads
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Rank: Super forum user
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Rank: Super forum user 
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an expolsion is just a very rapid fire
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Rank: Super forum user
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Sorry a really rapid fire(subsonic flame propagation) is a deflagration by contrast a detonation involves a supersonic shockwave passing through the material. It’s a much bigger bang.
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Rank: Super forum user
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An explosion is not just a rapid fire.
Fire
Explosion
Deflagration
Distinctly different, similarities, but different.
Speed of the shock wave etc is supersonic in an explosion, subsonic in a deflagration, a fire by itself doesn't have a shock wave.
See 'Handbook of fire and explosion protection principles' ISBN 978-1-4377-7857-1
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Rank: Super forum user
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I should know better than try to simplify on here.
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Rank: Super forum user
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It makes a big difference in the petro-chemical/oil & gas industry to know what accident and hazardous scenarios you are dealing with - fire loading/fire protection/blast protection of walls and pipelines etc gets expensive. Also effects the layout of plant and equipment.
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Rank: Super forum user
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Wot no mention of a BLEVE:-(
Boiling Liquid Expanding Vapour Explosion
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Rank: Super forum user
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That's just one type of fire/blast scenario - I was just making a general point, regarding the differences.
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Rank: Super forum user
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Except of course that the real damage is caused by the implosion following the rapid combustion of the vapours creating a vacuum within the cloud. Look at the Flixboro inquiry photographs and you will see the very significant bending of the lampposts towards the centre of the "blast" and not away from it.
Definitions cannot be hard and fast and there certainly are a number of intermediate points on what is essentially a continuous scale of severity. The blitzes of London and Dresden whilst fire based were ultimately far more severe than many explosions.
Distinguishing between flammable, highly flammable and explosive is always a matter of ignition temperature and speed of combustion and containment of combustion products. In open air unconfined gunpowder rapidly burns - it only explodes if confined in some way. Wonderfully thought provoking but one has to accept the nationally recognised definition at the end of the day whatever someone else may define as the boundary.
Bob
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