Adaptation to indoor air pollution
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Environment International, Vol. 18, pp. 43 - 54, 1992
Printed in the U.S.A. All fights reserved.
0160--4120/92 $5.00 +.00 Copyright © 1991 Pergamon Press pie
INTRODUCTION
Ever since the classical experiments of Yaglou (1936), standards for ventilation have primarily been based on people's perception of the air quality. Comfort criteria have often proved to be the most restrictive for indoor air quality. Ventilation requirements have been set up based on the first impression of the air quality although adaptation often modifies the perception considerably. It was felt to be unrealistic to tell people to disregard their first negative impression and wait a few minutes until they had adapted to the pollution. Furthermore, the available data quantifying the effect of adaptation were limited.
EI 8909-236M (Received 15 June 1989; accepted 29 June 1991)
The change in the perception of polluted air was studied during the first 15 rain of exposure in climate chambers. Subjects, 16 female and 16 male, ages 18-30 y, served as air quality judges during 42 exposures. They were exposed to different concentrations of human bioeffluents (500-4000 I.tL/L CO2), tobacco smoke (0.25-2.5 laL/L CO), and emissions from building materials (-). The subjects voted every 2 rain on scales for odor intensity and acceptability of the air quality, while they were exposed to constant levels of the air pollution. Perception of bioeffluents reached a low level independent of concentration after a few minutes. Adaptation to tobacco smoke caused acceptability to increase, but votes still depended on concentration. Ventilation for comfort may be reduced considerably if a few minutes of discomfort are acceptable or if the occupants are exposed to a gradually increased pollution level during the first 10 rain or more of their stay in a space.
44
L. Gunnarsen and P.O. Fanger
Earlier investigations of phenomena involving adaptation have concentrated on specific singlecomponent odorants and irritants (Cain 1985; Engen 1987; Ekman et al. 1967; Berglund 1978; Stone 1972). Cain (1985) presented a model for the time course of olfactory adaptation to single components. He found that perceived intensity reaches a stable level of approximately 40% of the initial magnitude after 3 min of adaptation. Pollution indoors is usually more complex comprising a large number of single pollutants. A person may experience changes in both the concentration and composition of indoor pollution. Perception of air pollution may depend on several adaptational phenomena. For some pollutants, the time effects may cause fewer dissatisfied persons after a short exposure, while dissatisfaction may grow after a longer period (one hour or more). In the present study, only the first 15 min of exposure were studied. Transients in air quality are experienced not only when air quality in a room is changing but also when persons walk from one room to another. Often transients are both qualitative and quantitative. This makes the real life situation complex. It is our aim to establish a model for the perception of air quality during transients. The purpose of the present investigation is to study discomfort caused by typical indoor pollution before, during, and after a transient period of adaptation. When entering a room, the air may seem unacceptable, but during an adaptational period, the sensation of odor may decrease while the irritation may increase or remain constant (Engen 1986). The combined effect of these two sensory processes will be quantified.
METHOD
through a perforated floor and left via ducts in the ceiling. The air was well mixed by a recirculation rate as high as 50 h -1. Outdoor air was supplied through a series of filters including activated carbon. The supply of outdoor air was controlled by individually calibrated arrangements of orifice plates. During all experiments, curtains were hung in the chambers dividing them into a section for judges and a section invisible to judges where pollution sources could be placed. The third chamber, designed for thermal environmental studies, was used as a reference (KjerulfJensen 1975). Air enters and leaves the chamber in the same way as in the twin chambers. Traditional materials are used in ductwork and the chamber is plastic-lined. The supply of outdoor air was 1000 L/s, or 30 L/s per person when 32 persons occupied the chamber. Temperatures in all chambers were kept constant at 22 °C (+0.3 °C). The humidity was in the range of 3-7 g/kg (20-40 %RH), and no attempt was made to control it.
Printed in the U.S.A. All fights reserved.
0160--4120/92 $5.00 +.00 Copyright © 1991 Pergamon Press pie
INTRODUCTION
Ever since the classical experiments of Yaglou (1936), standards for ventilation have primarily been based on people's perception of the air quality. Comfort criteria have often proved to be the most restrictive for indoor air quality. Ventilation requirements have been set up based on the first impression of the air quality although adaptation often modifies the perception considerably. It was felt to be unrealistic to tell people to disregard their first negative impression and wait a few minutes until they had adapted to the pollution. Furthermore, the available data quantifying the effect of adaptation were limited.
EI 8909-236M (Received 15 June 1989; accepted 29 June 1991)
The change in the perception of polluted air was studied during the first 15 rain of exposure in climate chambers. Subjects, 16 female and 16 male, ages 18-30 y, served as air quality judges during 42 exposures. They were exposed to different concentrations of human bioeffluents (500-4000 I.tL/L CO2), tobacco smoke (0.25-2.5 laL/L CO), and emissions from building materials (-). The subjects voted every 2 rain on scales for odor intensity and acceptability of the air quality, while they were exposed to constant levels of the air pollution. Perception of bioeffluents reached a low level independent of concentration after a few minutes. Adaptation to tobacco smoke caused acceptability to increase, but votes still depended on concentration. Ventilation for comfort may be reduced considerably if a few minutes of discomfort are acceptable or if the occupants are exposed to a gradually increased pollution level during the first 10 rain or more of their stay in a space.
44
L. Gunnarsen and P.O. Fanger
Earlier investigations of phenomena involving adaptation have concentrated on specific singlecomponent odorants and irritants (Cain 1985; Engen 1987; Ekman et al. 1967; Berglund 1978; Stone 1972). Cain (1985) presented a model for the time course of olfactory adaptation to single components. He found that perceived intensity reaches a stable level of approximately 40% of the initial magnitude after 3 min of adaptation. Pollution indoors is usually more complex comprising a large number of single pollutants. A person may experience changes in both the concentration and composition of indoor pollution. Perception of air pollution may depend on several adaptational phenomena. For some pollutants, the time effects may cause fewer dissatisfied persons after a short exposure, while dissatisfaction may grow after a longer period (one hour or more). In the present study, only the first 15 min of exposure were studied. Transients in air quality are experienced not only when air quality in a room is changing but also when persons walk from one room to another. Often transients are both qualitative and quantitative. This makes the real life situation complex. It is our aim to establish a model for the perception of air quality during transients. The purpose of the present investigation is to study discomfort caused by typical indoor pollution before, during, and after a transient period of adaptation. When entering a room, the air may seem unacceptable, but during an adaptational period, the sensation of odor may decrease while the irritation may increase or remain constant (Engen 1986). The combined effect of these two sensory processes will be quantified.
METHOD
through a perforated floor and left via ducts in the ceiling. The air was well mixed by a recirculation rate as high as 50 h -1. Outdoor air was supplied through a series of filters including activated carbon. The supply of outdoor air was controlled by individually calibrated arrangements of orifice plates. During all experiments, curtains were hung in the chambers dividing them into a section for judges and a section invisible to judges where pollution sources could be placed. The third chamber, designed for thermal environmental studies, was used as a reference (KjerulfJensen 1975). Air enters and leaves the chamber in the same way as in the twin chambers. Traditional materials are used in ductwork and the chamber is plastic-lined. The supply of outdoor air was 1000 L/s, or 30 L/s per person when 32 persons occupied the chamber. Temperatures in all chambers were kept constant at 22 °C (+0.3 °C). The humidity was in the range of 3-7 g/kg (20-40 %RH), and no attempt was made to control it.
