17.1 Introduction
This chapter is devoted to the provision of guidance on the protection against
lightning-related electric sparks to structures containing explosive or highly flammable
materials that can generate an explosive atmosphere. These materials can
take the form of solids, liquids, gases, vapours or dusts. In this chapter, ‘structures’
is the term used for vessels, tanks or other containers in which these materials
are contained.
An ignition source is anything that can heat even a small portion of a fuel to its autoignition
temperature. Owing to its high temperature, lightning and electric sparks
(such as electrostatic discharges) can generate ignition in a volatile atmosphere, and
thus cause fire and explosion. Ignitions with high pressure waves are termed
‘explosions’ and ignitions with minor pressure waves are known as ‘flash-fires’.
Despite the great variety of types of structure involved, the main causes of flash-fire
and explosion arising from lightning, which are common in many situations, are the
following [1]: