Dynamic elaboration on the Art & Science of Hazardous Area Protection
Hazardous Area & Zones
The term “ZONE” & its concept is a coordinated way to classify Hazardous Areas
Before we embark on our journey into the ZONES , let us update our information about the following terms :-
Flammable and inflammable do not mean the same thing. If something is flammable it means it can be set fire to, such as a piece of wood. However, inflammable means that a substance is capable of bursting into flames without the need for any ignition. …The opposite of both words is non-flammable.
To avoid the confusion of the prefix “in” (as in inflammable) which appears to be the OPPOSITE of flammable, the preferred term is “FLAMMABLE”
It is a mixture with Air, under atmospheric conditions, of Flammable substances, in the form of gas, vapour, dust, powder, fibres or flyings, which, after ignition permits self-sustaining flame propagation.
Explosive Gas Atmosphere have gas or vapours as the Flammable substance
Explosive Dust Atmosphere have dust, powder
An Area in which Explosive Gas Atmosphere is or may be expected to be present, in quantities such as to require special precautions for the construction, installation & use of the equipment.
The definition of Hazardous Area dose not quantify the following 2 parameters: –
The vagueness in the definition is given clarity by the concept of ZONES.
….. So let us see & visit the ZONES.
First an official definition.
Hazardous Area classification based upon the frequency of the occurrence and duration of an Explosive Atmosphere.
We will use the following guidelines for our journey.
Let us proceed
The first stop is the INDUSTRIAL LEVEL
The process area governed by Industrial Standards of IEC , ISO and other respective authorities and Industrial Safety protocols .
This is a SAFE or a NON-HAZARDOUS AREA .
We will not find any Zones at this level.
Proceeding further inside
Beyond or besides the Industrial Area there is a area marked as Hazardous Area .
Rating : Zone 2
That area in which an Explosive Gas Atmosphere , consisting of a mixture with air of Flammable substance in the form of gas, vapor or mist is not likely to occur in normal operation but, if it does occur , will persist for a short period only.