The present invention relates to cleaning compositions, in particular to cleaning compositions for use in heating, ventilation and air-conditioning (HVAC) installations. We describe an acidic cleaning composition concentrate comprising: at least one acid having a pKa.sub.1 of 4 or less, wherein the at least one acid is at least one organic acid and/or non-oxidising mineral acid; a rheology modifier, and a polar protic solvent. In some examples, compositions may also include at least one of one or more weak nitrogenous bases, one or more carboxylate salts and one or more surfactants.