Medical professionals are acquiring a significant amount of evidence to demonstrate that the quality of air found inside a building impacts the health of the occupants.
Indoor air is increasingly important because populations now spend a substantial fraction of time within buildings. In offices and factories as well as residences, retirement homes and day-care centres, indoor air quality affects people of all backgrounds, and especially those who are particularly vulnerable through their state of health or age. From a population health professional?s perspective, the management of indoor air quality is an important part of the overall picture.
High levels of relative humidity inside a building can result in the emergence of mould and mites. Furthermore, micro-bacterial contamination can result from many hundreds of species of bacteria that can multiply indoors when there is sufficient moisture available. Exposure to microbial contaminants is now well understood to be associated with respiratory symptoms, asthma and immunological reactions as well as allergies.
The role of Ventilation in a Building
Ventilation is intended to remove or dilute pollutants and to control the temperature and humidity in buildings. The level of ventilation needs to be sufficient either to remove The pollutants and humidity generated indoors or to dilute their concentrations to acceptable levels for the health and comfort of the occupants. A number of studies, e.g. [1] have shown an association between ventilation and health, although the precise relationship differs by study.
Ventilation can be achieved with a variety of natural and mechanical methods. Whilst, proper ventilation does indeed generally deliver health improvements, ventilation can also have adverse effects if not properly designed, maintained and Managed. It is possible for ventilation to allow the inflow of harmful substances that degrade the indoor air quality.
Ventilation particularly affects air and moisture flow through the building and poor ventilation may also result in moisture problems that degrade the structure. Ventilation changes pressure differences across a building and may cause or prevent the infiltration of pollutants from building structures or adjacent spaces.
In non-residential buildings (and also in hot climates), ventilation is often combined with air-conditioning, which further complicates the operation of these systems.
The addition of humidifiers to ventilation systems or as stand-alone units, can introduce a high humidity or micro-organisms that grow on components in humid locations, such as drip pans in air-conditioning units or humidifiers, as well as chemicals used for water treatment.
A number of studies show that the onset of symptoms of sick-building syndrome can be linked to the nature of the heating, ventilation and air-conditioning system [2, 3]. Air-conditioning is commonly associated with a measurable increase in the frequency of one or more sick-building syndrome symptoms in office buildings when compared to similar buildings with natural ventilation.
There is now a significant body of evidence to suggest that improved hygiene, installation, operation and maintenance of air-handling systems is particularly significant in reducing the negative effects of these systems [2, 4, 5, 6, 7, 8].
So, what are the implications of this evidence for an employer whose employees are accommodated in an air-conditioned environment?
Simply, that with a regular programme of maintenance in place, many of the unwanted effects highlighted above, such as moisture and microbial contamination can be minimised to a level that does not impact on the occupants health. But conversely, should the air-conditioning system be neglected, then there is a potential health impact on the building occupants.
References
[1] Sundell J, Levin H (2007). Ventilation rates and health: report of an interdisciplinary review of the scientific literature. Final report. Atlanta, American Society of Heating, Refrigerating and Air-conditioning Engineers.
[2] Mendell MJ, Smith AH (1990). Consistent pattern of elevated symptoms in airconditioned office buildings: a reanalysis of epidemiologic studies. American Journal of Public Health, 80:1193?1199.
[3] Seppanen OA, Fisk WJ (2002). Association of ventilation system type with SBS symptoms in office workers. Indoor Air, 12:98?112.
[4] Sieber WK et al. (1996). The National Institute for Occupational Safety and Health indoor environmental evaluation experience: part three ? associations between environmental factors and self-reported health conditions. Applied Occupational and Environmental Hygiene, 11:1387?1392.
[5] Seppanen O, Fisk W, Mendell M (1999). Association of ventilation rates and CO2 concentrations with health and other responses in commercial and institutional buildings. Indoor Air, 9:226?252.
[6] Mendell MJ et al. (2003). Environmental risk factors and work-related lower respiratory symptoms in 80 office buildings: an exploratory analysis of NIOSH data. American Journal of Industrial Medicine, 43:630?641.
[7] Mendell MJ et al. (2006). Indicators of moisture and ventilation system contamination in US office buildings as risk factors for respiratory and mucous membrane symptoms: analyses of the EPA BASE data. Journal of Occupational and Environmental Hygiene, 3:225?233.
[8] Mendell MJ et al. (2008). Risk factors in heating, ventilating, and air-conditioning systems for occupant symptoms in US office buildings: the US EPA BASE study. Indoor Air, 18:301?316
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Iain Jones works for Pro-Duct Clean Ltd a commercial air duct cleaning company. Pro-Duct Clean serve industrial customers in the UK.
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