Asthma

Quansah et al. (2012) concluded that 'dampness and moulds in the home are determinants of developing asthma', with OR 1.33 for dampness, 1.29 for visible mould and 1.73 for mould odour. WHO lists asthma among the outcomes with sufficient evidence. An air conditioner is not a 'damp home', but it is a point source of spores and MVOC in the room where one sleeps 8 hours a night. For an asthma patient, physicians recommend reducing all exposure sources – sanitising the unit is one of the easy ones.

Split-unit studies (Liu 2025; Shiraishi 2023; Hamada 2002) consistently find Cladosporium, Alternaria, Aspergillus and Penicillium, and WHO and IOM describe them as major respiratory allergens associated with asthma exacerbations in sensitised people. Liu et al. estimate that about 64% of the genera found on filters include pathogenic or allergenic species. A positive mould allergy test in a family member is a clear reason for twice-yearly sanitising and filters cleaned every 2 weeks.

The ECRHS study (Zock et al., JACI, 2009) found that domestic use of hypochlorite bleach is associated with respiratory symptoms in adults, even though it reduces atopic sensitisation. EPA explicitly recommends against bleach as routine practice in mould cleanup. In a split, chlorine sprayed or poured through the grille evaporates straight into the air you breathe, corrodes aluminium and copper and does not remove biofilm. Professional sanitising uses aluminium-compatible cleaners and disinfectants, applied and rinsed inside the collection cover.