For the purposes of this Part of this Act—
any installation for the combustion of fuel which is used in any manufacturing or trade process, or for working engines by steam, and which does not so far as practicable prevent the emission of smoke to the atmosphere and
any chimney (not being the chimney of a private house) emitting smoke in such quantity as to be a nuisance,
shall be statutory nuisances and are in this Act referred to as " smoke nuisances."