1. Mobile or transportable furnaces

(a) Providing a temporary source of heat or power during any building operation or work of engineering construction (within the meaning of section 176 of the Factories Act 1961);

(b) providing a temporary source of heat or power for investigation or research;

(c) providing heat or power for the purposes of agriculture (within the meaning of section 109(3) of the Agriculture Act 1947)

2. Furnaces, other than furnaces designed to burn solid matter at a rate of 0.989 tonne an hour (or 989 kilogram an hour) or more, which fall within any of the following descriptions and in which the matter being heated does not contribute to the emission of grit and dust—

(a) furnaces burning liquid matter, gas, or liquid matter and gas;

(b) hand-fired sectional furnaces designed to burn solid matter at a rate of not more than 122 kilogram/square meter/hour of grate surface;

(c) magazine type gravity-fed furnaces designed to burn solid matter at a rate of not more than 122 kilogram/square meter/hour of grate surface;

(d) furnaces fitted with an under-feed stoker designed to burn solid matter at a rate of not more than 122 kilogram/square meter/hour of the plan area of the combustion chamber;

(e) furnaces fitted with a chain grate stoker designed to burn solid matter at a rate of not more than 122 kilogram/square meter/hour of grate surface;

(f) furnaces fitted with a coking stoker designed to burn solid matter at a rate of not more than 122 kilogram/square meter/hour of the area covered by the fire bars excluding the solid coking plate

Any purpose except the incineration of refuse