Flammability & Combustibility

Introduction 

What is Flammability?

    If the material easily catches fire under normal circumstances and with the help or minimal ignition source, just a spark is sufficient. Eg: Propane.

What is Combustibility?

    Material like wood and paper require vigorous condition to catch fire, a simple spark is not enough.

Flammability (or) Combustibility

Ability of any substance to catch fire and burn. It catches fire easily and burn which is called flammability or combustibility. Eg: paper, kerosene, petrol, LPG.

Non-Flammability (or) Incombustibility

Which do not catch fire is called incombustibility or non-flammability. Eg: water, sand.

The mixture of flammable vapor and air which can catch fire in the presence of ignition source is called flammable mixture and the ability of that flammable substance/material to burn is called flammability.

Limits of flammability

i.       Lower Flammability/Explosive Limit (LEL): [˃10%] The minimum percentage of flammable vapor in air which can catch fire in the presence of ignition source. 

ii.       Upper Flammability/Explosive Limit (UEL): [˂20%] The maximum percentage of flammable vapor in air which can catch fire in the presence of ignition source. 

iii.     Lean or Weak Flammable Mixture: The concentration which are nearer to lower flammability limit are called Lean Flammable Mixture.

iv.     Rich or Strong Flammable Mixture: The concentration which are nearer to upper flammability limit is called Rich Flammable Mixture.

Flammability Table

          All the chemical which has a flash point below 100^oF is flammable and above 100^oF is combustible.

          Where,
                             FP     – Flammable Point

                             BP     – Boiling Point

                             NFPA – National Fire Protection Association