Gasoline has a flammability range of 1.4 to 7.6 percent. This means it will ignite when there is 1.4 parts of gasoline mixed with 100 parts air. With this in mind, 1.4 percent is known as the lower flammable limit and 7.6 percent is the upper flammable limit of the flammable range. A product mixed with air below the low end of its flammable range is too lean to burn. A flammable liquid which exceeds its upper flammable limit is too rich to ignite.
Ethylene oxide is extremely flammable.
It has a flammable range of 3.6 to 100 percent. This means it can burn even if there is no air. Gasoline has a narrow flammable range and is metered precisely in a vehicle's carburetor to obtain the desired flammable range. A vehicle will have trouble operating if the carburetor meters too much gasoline. This is referred to as a rich mixture, which is too concentrated for ignition by the spark plugs.