What is the exception condition under which elevation of the ignition source is not required?

The exception condition under which elevation of the ignition source is not required pertains to flammable vapor ignition resistant appliances. These appliances are designed specifically to mitigate the risk of ignition from flammable vapors. They incorporate features that prevent ignition sources from coming into contact with flammable vapors, thus eliminating the necessity for elevation.

In typical applications, elevating ignition sources helps to minimize the risk by keeping them above potential vapor levels. However, flammable vapor ignition resistant appliances are constructed with safety measures that counteract this risk, allowing them to operate safely at or near ground level without needing the elevated installation that other appliances might require. This unique design and intention behind these appliances justify the exception, simplifying installation requirements while maintaining safety standards.