Through the study of :-

• Formation of Hazardous Area

• Ignition

• Upper & Lower Explosive Limits

• Prevention

WORKING OF A FIRE TRIANGLE

Consider…… an industrial facility with

A source of Flammable Gas or Vapors.

(Referred to as FUEL in this study)

OXYGEN(From the surrounding Air)

FUEL

12.00

OXYGEN FUEL

OXYGEN is present in the air

12.00

Source of release .

OXYGEN FUEL

A mixture of flammable gas & oxygen starts to form an explosive GAS-AIR MIXTURE

12.10

OXYGEN FUEL

12.20

The volume of the GAS-AIR Mixture increases with time

OXYGEN FUEL

12.30

The GAS-Air mixture is explosive and is now occupying the most of the space

OXYGEN FUEL

12.31

ANY spark can ignite this AIR GAS MIXTURE.This spark can be from a number of sources.

IGNITION

The GAS-Air mixture is explosive and is now occupying the most of the space

OXYGEN FUEL

12.31

ANY spark can now ignite this AIR GAS MIXTURE.This spark can be from a number of sources.

IGNITION

The GAS-Air mixture is explosive and is now occupying the most of the space near & around the leaking GAS cylinder

OXYGEN FUEL

IGNITION

ANALYSISBefore the explosion .

A mixture of flammable GAS & oxygen (from air) was being formed and gaining more

volume with passage of time .

But still there was no explosion because there was no SPARK to ignite the mixture.

With an accidently generated spark the MIXTURE was ignited and resulted in an

EXPLOSION.

The effects of the heat and flame covered the whole of the area previously occupied by the

GAS-AIR mixture .

AT this point , we will stop our clock and go , one

slide back to analyze the situation.

OXYGEN FUEL

IGNITION

We can easily recognize the EXPLOSIVE TRIANGLE present in this situation

and responsible for the explosion.

OXYGEN + FUEL + SPARK

OXYGEN FUEL

IGNITION

The Explosive Triangle resulted in an explosion due to the following favorable

condition :

The GAS-AIR mixture was in proper proportion (NOT RICH & NOT LEAN)

Technically the Mixture composition was within the EXPLOSIVE LIMITS.

OXYGEN FUEL

12.30

High concentration of air and

very low concentration of

FUEL in this region so there

will be no explosion even

with a spark .

Explosive Triangle will simply

not exist.

The mixture is too thin or

lean.

This is the START of the

LOWER EXPLOSIVE LIMIT

High concentration of FUEL

and very low concentration of

AIR in this region so there

will be no explosion even

with a spark .

Explosive Triangle will not

exist.

The mixture is too rich.

This the START of the

UPPER EXPLOSIVE

LIMIT

The

mo

st f

avo

rab

le c

on

cen

trat

ion

of

AIR

–FU

EL M

ixtu

re

OXYGEN FUEL

12.30

This concentration of the GAS-AIR Mixture is most dangerous and may explode if ignited

MOST EFFECTIVE BASIC RULE OF PREVENTION/ SAFETY in HAZARDOUS AREAS

STOP / Prevent the formation of FIRE TRIANGLES

Guide lines : IEC 60079