Flammability Limits Analyzer

Estimate the lower and upper flammability limits of a fuel blend in air with Le Chatelier's rule and the calculated adiabatic flame temperature method, the limiting oxygen concentration with nitrogen or carbon dioxide, and the fuel–oxygen–inert flammability envelope, with optional explosion limits from a kinetic mechanism.
Estimated minimum cost: $—

Examples

Fuels

A fuel blend from the built-in table of 30 gases and vapors (lower and upper limits in air from USBM Bulletin 627). Mole fractions are fractions of the fuel blend, not of the fuel–air mixture.

Fractions sum to 1

Conditions and envelope

Initial temperature and pressure of the mixture, and the inert used for the limiting oxygen concentration and the envelope.

Reading the results

  • These are screening estimates, not measured limits (ASTM E681) or a substitute for NFPA 68 / NFPA 69 or local code compliance.
  • The calculated limiting oxygen concentration sits about 2 points of O₂ below measured values for methane (Bulletin 627, fig. 28): the conservative side for inerting.
  • Hydrogen and fuels with decomposition flames (acetylene, ethylene oxide, hydrazine) are flagged: their tabulated limits are not thermal limits.

Explosion-limit peninsula

Optional p–T map of explosion limits from 0-D ignition runs with a kinetic mechanism, such as the classic H₂/O₂ peninsula. A point explodes when the mixture heats by half its adiabatic temperature rise (50–400 K) before the end time; points the solver could not settle are reported as unresolved. Homogeneous reactors have no wall chain termination, so the lowest-pressure (first) limit is not modelled.