 This weakness may be eliminated by designs where the fuel is preheated well above its ignition temperature, so that its cooling during its dispersion still results in a minimal ignition delay on mixing.The continual combustion of the outer layer of fuel molecules as they come into contact with the air, generates additional heat which maintains the temperature of the interior of the fireball, and thus sustains the detonation.In confinement, a series of reflective shock waves are generated, which maintain the fireball and can extend its duration to between 10 and 50 ms as exothermic recombination reactions occur.