The most common moulds affecting residential properties in the U.K are Trihoderama, Penicillium, Pullularia and Aspergillus spp. Mould spores are omnipresent in the air, in order to propagate they require a source of ‘free water’, that is to say, a source of moisture that can be physically touched, unlike for instance rising damp, which is capillary bound moisture, and which cannot be physically felt, nor give rise to mould growth. The three main sources of ‘free water’ in a domestic dwelling are: a plumbing leak, penetrating damp and condensation.