Recognising mould

In buildings, mould tends to form green, grey or black marks (other colours are yellow, orange, brown and white) and produce an earthy odour.

Mould is sometimes confused with saltpetre, which is a white mineral compound that appears on the surface of certain materials caused by high humidity. Saltpetre is therefore an indicator that moisture is present that could encourage the development of mould, but this white mineral compound does not, in itself, pose a considerable risk to health.

Mould

Saltpetre