Ignition may occur immediately, or may be delayed by up to tens of minutes, all depending on the circumstances. The most dangerous situation will occur if a large combustible premixed fuel-air cloud is formed and ignites. The time from release start to ignition can be from a few seconds up to tens of minutes. The amount of fuel can be from a few kilograms up to several tons. The consequences of gas explosions range from no damage to total destruction.
Fires are very common events after gas explosions.
When a cloud is ignited the flame can propagate in two different modes through the flammable parts of the cloud. The deflagration mode of flame propagation is the most common. The shock wave and the combustion wave are in this case coupled. Gas explosion in a partly confined area with process equipment. In a building or in an offshore module with process equipment as shown schematically in Figure 1.2, the flame may accelerate to several hundred meters per second.