When LNG spills in a accident but is not ignited immediately, the vapor cloud will mix with air and form a combustible mixture whose size, shape, and homogeneity depends on the amount of material spilled, the rate of vapor evolution, and the atmospheric and environmental conditions. If the combustible mixture subsequently ignites, several sources of damage are theoretically possible and therefore must be examined. Damage can result from overpressure or thermal energy. Overpressure can be generated if there is either direct shock initiation of a detonation or if there is sufficient flame acceleration. I will divide damage from thermal energy into two categories also--that occuring within the burn zone itself and that occuring outside of it.