Sick building syndrome

The Seppänen & Fisk (2002) review, cited by LBNL, shows SBS symptom prevalence (eye and nasal irritation, headache, fatigue) is 30–200% higher in air-conditioned buildings than in naturally ventilated ones, confirmed in tropical climates (Graudenz 2005). Studies from Italy (1992) and India (2023) report high prevalence and absenteeism in air-conditioned buildings. The most plausible explanation, supported by Menzies (2003), is microbial contamination of wet coils and pans. For offices with many splits, annual sanitising and ventilation are measures with an excellent cost/benefit ratio.

Mendell et al. (Indoor Air, 2008) analysed 100 office buildings in the EPA BASE study: no scheduled HVAC inspections was associated with OR 2.2 for eye symptoms, 1.6 for cough and 1.5 for upper respiratory symptoms; infrequent coil/pan cleaning with OR 1.6 for headache; poorly maintained humidification with OR 1.8 for fatigue/difficulty concentrating. It is among the most direct evidence that maintenance frequency shows up in occupant symptoms. For companies, a documented maintenance programme is not just technical but an occupational-health measure.

The double-blind Menzies et al. trial (The Lancet, 2003) with 771 workers in three buildings switched UV-C lamps on cooling coils and drain pans on and off without occupants' knowledge: microorganisms on irradiated surfaces fell by about 99%, and work-related symptoms by about 20% overall, respiratory symptoms by about 40% and mucosal symptoms by about 30%. WHO cites this study as evidence that microbes in HVAC systems affect occupant health. The conclusion for splits: if removing microbes from the coil reduces symptoms, mechanically cleaning the same coil serves the same goal.