Class of Fire and type of Extinguishers used

Fire On Board Is A Very Critical Situation. Correct Knowledge About The Class Of Fire And What Type Of Extinguishers To Be Used Can Help People On Board  to Fight Fire And Prevent Its Spread.

Q1.  What Is A Fire & How It Occurs?
Fire Is A Chemical Reaction, Giving Off Heat And Light.  
For Fire To Occur Three Elements Are Required :
I) Oxygen
Ii) Fuel 
Iii)Heat
 
The Above 3 Elements Form The Fire Triangle.  If Any One Of The Three Sides Of The Triangle Is Removed, The Triangle Will Collapse And Hence There Will Not Be Any Combustion.  The Principle Of Fighting Fire Is To Remove One Side Of The Fire Triangle.

Q2. What Do You  mean By Fire Tetrahedron?
"Chain Reaction" Is The Fourth Element Added To The Triangle To Define A Continuously Burning Fire, Which Is Known As The Fire Square Or A Tetrahedron.  

 Q3. What Are The Basic Ways To Fight Fire ?
1. Starving :  By Which The Fire Triangle Is Starved Of The Fuel Or Inflammable Material.  Remove The Inflammable Material And The Fire Will Burn Itself Out.
2. Smothering :  Is Like Asphyxiation - Take The Breath Out.  If There Is No Oxygen In The Air We Will Not Be Able To Live.  Likewise For Fire Oxygen Is Very Important And If That Element Is Removed Or Reduced To Below 15% Then The Fire Will Be Put Off.  Examples Of Smothering Agents Are CO2, Inert Gas, Foam.
3. Cooling :  If The Substance Is Cooled Until It Does Not Give Off Sufficient Vapours To Support Combustion, Then The Fire Will Be Extinguished.  Water Is A Good Example Of A Cooling Agent.
4. Inhibition :  Is The Process Of Interfering With And Stopping The Chemical Reaction In The Fire.

We Have Seen The Four Basic Ways Of Fighting Fire. The Method Of Extinguishing A Fire Depends On The Class Of Fire.  For Example, In Case Of An Oil Fire, Water Will Not Be Useful Though It Is The Best Cooling Agent. We Must Understand The Types Of Fire And The Method By Which To Extinguish.  

Q4. Describe The Classification Of Fire & Extinguishing Medium Used 
Class A Type Fire Involvs Wood, Paper,textiles, Fabrics, Plastics Etc. Water, CO2 And Foam Is  recommended To Be Used In Special Circumstances
Class B Type Fire Involving Combustible Liquid Or Liquefiable Solids. Water Spray, Foam, Dry Chemical Powder (DCP),etc Recommended To Be Used In These Circumstances.
Class C Type Fires Involving Gases Or Liquefied Gases. Shut Off The Supply Use Chemical Dry Powder To Extinguish These Type Of Fires.
Class D Type Fires Involving Metals. Special Dry Extinguishing Medium To Be Medium Used.

Some Sources Regard Electrical Fires As A Different Class Of Fire And In Such A Case Only Dry Powder Extinguisher Or CO2 Extinguisher Should Be Used.

Q5. What Type Of Extinguisher Found On Board Vessels ?
Normally Four Types Of Portable Extinguishers Are Found On Board For Extinguishing A Fire :
1. Foam Extinguishers
2. CO2 Extinguishers
3. Dry Chemical Powder (DCP) Extinguishers 
4. Water Extinguishers