Skin squames (cells that peel off from the skin surface) are a source of food for the bacteria found in air-cooling units, which produce odours even in a dust-free air-conditioning system, a study by Hong Kong Baptist University scholars revealed. This research is the first to show that the accumulation and bacterial degradation of skin squames in air-cooling units is positively correlated to the complaints of a urine-like smell in air-conditioned areas.