EFFECT OF AIR HUMIDIFICATION ON THE SICK BUILDING SYNDROME AND PERCEIVED INDOOR AIR-QUALITY IN HOSPITALS - A 4 MONTH LONGITUDINAL-STUDY

The sensation of dryness and irritation is essential in the sick build ing syndrome (SBS), and such symptoms are common in both office and ho spital employees. In Scandinavia, the indoor relative humidity in well ventilated buildings is usually in the range 10-35% in winter. The ai m of this study was to evaluate the effect of steam air humidification on SBS and perceived air quality during the heating season. The study base consisted of a dynamic population of 104 hospital employees, wor king in four new and well geriatric hospital units in Sweden. Air humi dification raised the relative air humidity to 40-45% in two units dur ing a four months period, whereas the other two units served as contro ls with relative humidity from 25-35%. Symptoms and perceived indoor a h quality were measured before and after the study period by a standar dised self administered questionnaire. The technical measurements comp rised room temperature, air humidity, static electricity, exhaust air flow, aerosols, microorganisms, and volatile organic compounds in the air. The most pronounced effect of the humidification was a significan t decrease of the sensation of air dryness, static electricity, and ai rway symptoms. After four months of air humidification during the heat ing season, 24% reported a weekly sensation of dryness in humidified u nits, compared with 73% in controls. No significant changes in symptom s of SBS or perceived air quality over time were found in the control group. The room temperature in all units was between 21-23 degrees C, and no significant effect of air humidification on the air concentrati on of aerosols or volatile organic compounds was found. No growth of m icroorganisms was found in the supply air ducts, and no legionella bac teria were found in the supply water of the humidifier. Air humidifica tion, however, significantly reduced the measured personal exposure to static electricity. It is concluded that air humidification during th e heating season in colder climates can decrease symptoms of SES and p erception of dry air.