Inflammable vs. combustible
The French words inflammable and combustible both describe materials that can burn, but they differ significantly in how easily they catch fire. While an inflammable substance ignites rapidly and easily with a simple spark or small flame, a combustible material requires higher temperatures or more sustained heat to start burning.
Inflammable
The word inflammable refers to substances that are highly flammable and catch fire very quickly and easily, often instantly at normal working temperatures.
L'essence est un liquide très inflammable qu'il faut manipuler avec précaution.
(Gasoline is a highly flammable liquid that must be handled with care.)
Gardez ce vaporisateur loin des flammes car son contenu est inflammable.
(Keep this spray away from flames because its contents are flammable.)
Les vapeurs dégagées par ce solvant industriel sont extrêmement inflammables.
(The vapors released by this industrial solvent are extremely flammable.)
Le papier journal sec est une matière facilement inflammable.
(Dry newspaper is an easily flammable material.)
Il est interdit de transporter des matières inflammables dans les bagages en soute.
(It is forbidden to transport flammable materials in checked baggage.)
Combustible
The word combustible describes materials that are capable of burning but generally require a higher temperature, more effort, or more time to ignite compared to highly flammable substances.
Le bois de chauffage est un excellent matériau combustible pour les froides nuits d'hiver.
(Firewood is an excellent combustible material for cold winter nights.)
Le charbon est un solide combustible qui a été largement utilisé pendant la révolution industrielle.
(Coal is a solid combustible that was widely used during the industrial revolution.)
Assurez-vous de ne jamais stocker de déchets combustibles à côté du four à bois.
(Make sure you never store combustible waste next to the wood stove.)
Cette huile de moteur lourde est combustible mais elle ne prendra pas feu à température ambiante.
(This heavy motor oil is combustible but it will not catch fire at room temperature.)
Les pompiers ont enlevé toute la végétation combustible autour de la maison pour la protéger.
(The firefighters removed all the combustible vegetation around the house to protect it.)
Summary
In summary, use inflammable for dangerous materials that catch fire effortlessly like alcohol or gas, and choose combustible for everyday materials that can burn but need a strong heat source to ignite, like wood or heavy oil. Remember that while all inflammable items are technically combustible, regular combustible items are not inflammable.