What is meant by flammability limits?

Flammability limits or explosive range: The entire range of concentrations of a mixture of flammable vapor or gas in air (expressed as volume percent) over which a flash will occur or a flame will travel if the mixture is ignited.

What are the upper and lower limits of flammability?

The upper flammability limit is defined as the concentration of the most concentrated mixture that is flammable and the lower flammability limit as the concentration of the most dilute fuel-air or fuel-diluent mixture that is flammable.

What are the flammable limits of an atmosphere?

Atmospheres with a concentration of flammable vapors at or above 10 percent of the lower explosive limit (LEL) are considered hazardous when located in confined spaces. However, atmospheres with flammable vapors below 10 percent of the LEL are not necessarily safe. Such atmospheres are too lean to burn.

Why are flammability limits important?

The flammability limits are important to note, due to easy combustion or making safe mixtures. Optimum combustible mixtures are important for internal combustion engine’s ignition. For example, lower flammability limit of Jet A fuel in the air at sea level is about 0.7\%. However the optimum would be about 4.8\%.

What is the upper explosive limit?

The highest concentration of a gas or vapor (percentage by volume in air) above which a flame will not spread in the presence of an ignition source (arc, flame, or heat). Concentrations higher than UEL are “too rich” to burn.

What is the maximum allowable lower explosive level LEL?

The Lower Explosive Limit (LEL) is the lowest concentration of a gas or vapour that will burn in air. The Lower Explosive Limit (LEL) varies from gas to gas, but for most flammable gases it is less than 5\% by volume.

What are the flammability limits of a methane air mixture?

Note!

Fuel Gas	“Lower Explosive or Flammable Limit” (LEL/LFL) (\% by volume of air)	“Upper Explosive or Flammable Limit” (UEL/UFL) (\% by volume of air)
Methane	4.4	16.4
Methylamine	4.9	20.7
Methyl acetate	3	16
Methyl alcohol, Methanol	6.7	36

What is the difference between flammability and explosion limits?

Flammability limits also depend on the type of atmosphere (for example, limits are much wider in oxygen than in air), the pressure, and the temperature of atmosphere. Explosion limits usually refer to the range of pressure and temperature for which an explosive reaction at a fixed composition mixture is possible.

How do you calculate explosive limits?

To compute the LEL of any gas in air, divide the unknown concentration by the LEL listed in the NFPA Handbook. 100\% LEL’s for 9 of Gasco’s more common gasses are shown in the table to the left. For example, if you take 2.5\% Methane in air and divide it by 100\% LEL of methane (5\%), the result is 50\% LEL.

What is the lower flammability limit of propane?

A: The lower explosive limit (LEL) of a gas or a vapour, is the lowest concentration (in air) that is needed for the gas to ignite and explode. For example, propane can explode when it reaches 2.1 per cent of the air, by volume. At 2.1\%v/v, propane has reached 100\% of its lower explosive level.

What does flammability limit stand for?

What Does Flammability Limit Mean? Flammability limit refers to the upper or lower limits of the gaseous or vaporized fuel or combustible material at a fixed temperature and pressure that can lead to flame propagation, detonation or an explosion. Fuel or combustible concentrations outside the both limits are considered to be non-flammable.

What is the definition of flammable limits?

Flammable (explosive) Limit. The range of a gas or vapor concentration that will burn or explode if an ignition source is introduced. Limiting concentrations are commonly called the “lower explosive or flammable limit” (LEL/ LFL ) and the “upper explosive or flammable limit” (UEL/UFL). Below the explosive or flammable limit,…

What is the upper flammable limit (UFL)?

What Does Upper Flammable Limit (UFL) Mean? The upper flammable limit (UFL) is the highest percentage of a vapor or gas in the atmosphere that will result in a flammable response when an ignition source is introduced. The concentration of a gas or vapor may be beyond the upper flammable limit, at which point it is too concentrated to burn.

What is the flammability range?

Flammable Range. The range of flammable vapor or gas-air mixture between the upper and lower flammable limits is known as the ‘flammable range’, also often referred to as the ‘explosive range’. For example, the lower limit of flammability of acrylonitrile at ordinary ambient temperatures is approximately 3 percent vapor in air by volume,…