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Combustion & Flammability Calculator

Calculate flammability limits (LEL/UEL), stoichiometric air, and combustion products for fuel gas, per NFPA 68/69.

NFPA 68NFPA 69API 521
Calculation Mode:
Look up flammability limits and calculate stoichiometric air for a single component

Pure Component

Operating Conditions

°F
LEL/UEL vary with temperature
psia
Standard: 14.696 psia. UEL increases at elevated pressure.

Engineering Basis

Le Chatelier's Mixing Rule
1/LEL_mix = Σ(y_i / LEL_i)

Calculates flammability limits for gas mixtures from pure component limits weighted by mole fractions.

Stoichiometric Combustion
CₙHₘ + (n + m/4)O₂ → nCO₂ + (m/2)H₂O

Complete combustion requires exact oxygen ratio. Excess air ensures complete burn.

Common Flammability Limits

Methane5.0 – 15.0%
Ethane3.0 – 12.4%
Propane2.1 – 9.5%
Hydrogen4.0 – 75.0%
H₂S4.0 – 44.0%

Frequently Asked Questions

What does the Combustion & Flammability Calculator do?

It calculates flammability limits (LEL/UEL), stoichiometric air requirements and combustion products for hydrocarbon mixtures per NFPA 68/69.

What are LEL and UEL?

LEL (Lower Explosive Limit) and UEL (Upper Explosive Limit) define the concentration range in which a gas-air mixture is flammable.

What standards does this flammability calculator follow?

The calculator follows NFPA 68 and NFPA 69 standards for combustion and flammability analysis of natural gas and hydrocarbon mixtures.