Explosion of gases in boiler flues (i.e. pipes). It is the result of ignition and not of the sudden release of internal pressure as in the case of a steam boiler explosion. The boiler and pressure plant policy can be extended to cover the explosion of gas in the furnaces or flues of the plant. Cover follows the terms of the boiler policy and therefore covers self-damage and the consequences thereof in terms of surrounding property and third party risks.