Parine, N. I; (1997) The human response to indoor air quality and the significance of the olf and decipol units. Doctoral thesis (Ph.D), UCL (University College London).

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Abstract

Historically, odour has been used as an indicator of a building's ability to provide occupants with an acceptable air quality. Humans are capable of sensing ambient air by multiple sensory reaction including olfaction, pungency, air movement, humidity and thermal sensation. In 1936 Yaglou and colleagues established that approximately 8 l/s per clean healthy adult was required to maintain the air as 'acceptable' and this level has been adopted by most developed countries since this time. However, consideration was given to establishing lower ventilation rates during the 1970's as a result of the energy crisis. Following this period, building occupants were found to be suffering from symptoms now referred to as 'the sick building syndrome'. One scenario, still largely unproven, suggests that the symptoms are due to reduced ventilation rates and the increase in synthetic materials in buildings, which has resulted in the build-up of a cocktail of irritants. Since 1981 ASHRAE has recommended the use of untrained panels of humans to rate the acceptability of a building's air quality, where less than 20% dissatisfaction is regarded as acceptable. In 1988, two new units of 'perceived air quality' were introduced; the olf and the decipol. It is argued that as humans are capable of detecting extremely low concentrations of many indoor pollutants, human olfaction should be employed to judged the 'acceptability' of indoor air. Recently this approach has been modified by relating the 'annoyance' produced by standard concentrations of acetone with the 'annoyance' from a building's air using a trained panel. Analysis of the fundamental basis behind the olf, the decipol and their application are presented in this thesis and reveals several problems in the design and implementation of the new units. These focus on the suggested precise relationship between the number of persons dissatisfied with the air quality and the ventilation rate expressed in litres per second per olf unit established using a two-point odour acceptability scale. Analysis of human perception to a wide variety of air quality responses from occupants in eight UK office buildings indicate a large level of dissatisfaction with indoor air quality but they did not indicate that this was due to odour. Physical monitoring in an air-conditioned office building in central London, questionnaire analysis of the occupants and the air quality responses of both trained and untrained 'sniffers' has shown the following: Reducing the ventilation rate by half did not result in any measurable change in human perception of air quality when carried out in a longitudinal blind study. There is a significant difference between occupant, trained and untrained panel's perception of indoor air quality. Outside air used to dilute pollutants was perceived as highly unsatisfactory by both trained and untrained panels which questions it use as a base level by which to judge internal air quality. Odour is not perceived as a major problem whereas indoor air quality is. This questions the use of odour as a surrogate for acceptable air quality. The level of dissatisfaction with indoor air quality as established by trained and untrained panels showed no correlation with the occupant level of dissatisfaction. The costly use of a trained panel is therefore challenged.

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