The performance and subjective responses of call-center operators with new and used supply air filters at two outdoor air supply rates Introduction Recent experiments have shown that increasing out- door air supply rate or removing sources of indoor pollution improves the perceived air quality (PAQ), reduces some Sick Building Syndrome (SBS) symptoms and improves the performance of typical office tasks (Wargocki et al., 1999, 2000a). The observed effects on PAQ and SBS symptoms are compatible with the results of many field studies (Norba¨ck and Torge´n, 1989; van Beuningen et al., 1994; Seppa¨nen et al., 1999; Pejtersen et al., 2001; Wargocki et al., 2002a), but there is insufficient information from field studies about the resulting effects on office productivity. The effects on performance reported by Wargocki et al. were observed using female subjects who were especi- ally recruited for the study. They performed simulated office work in exposures lasting only 4.6 h, in a test chamber resembling a real office. The observed effects on performance therefore require validation in actual office buildings with office employees performing real work and repeatedly exposed in their normal office environment for a full day at a time, 5 days a week. It is difficult to reliably quantify the performance of real office tasks. So far at least four very different metrics of productivity appear to have been used to investigate indoor environmental effects in the field: embedded neurobehavioral tests (Nunes et al., 1993); short-term sick leave (Milton et al., 2000); case-hand- ling time for insurance claims (Kroner and Stark- Martin, 1994); and the performance of operators in a call-center (Burton et al., 2001; Federspiel et al., 2002; Fisk et al., 2002; Niemela¨ et al., 2002; Tham et al., 2003). The last metric is an especially promising measure of office performance as work performed by operators is a good paradigm for many other kinds of Abstract A2 · 2 replicated field intervention experiment was conducted in a call-center providing a telephone directory service: outdoor air supply rate was adjusted to be 8% or 80% of the total airflow of 430 l/s (3.5 /h) and the supply air filters were either new or had been in place for 6 months. One of these independent variables was changed each week for 8 weeks. The interventions did not affect room temperature, relative humidity or noise level. The 26 operators were blind to conditions and each week returned questionnaires recording their environmental perceptions and Sick Building Syndrome (SBS) symptoms. Their performance was continuously monitored by recording the average talk-time every 30 min. Replacing a used filter with a clean filter reduced talk-time by about 10% at the high ventilation rate but had no significant effect at the low rate. Increasing the outdoor air supply rate reduced talk-time by 6% with a new filter in place but increased talk-time by 8% with a used filter in place. The interventions also had significant effects on some SBS symptoms and environ- mental perceptions. The present results indicate that increasing outdoor air supply rate and replacing filters can have positive effects on health, comfort and performance. Pawel Wargocki, David P. Wyon and P. Ole Fanger International Centre for Indoor Environment and Energy, Technical University of Denmark, Lyngby, Denmark Keywords: Call-center, Filter, SBS symptoms, Office work, Outdoor air supply rate, Productivity Pawel Wargocki International Centre for Indoor Environment and Energy, Technical University of Denmark, Building 402, DK-2800 Lyngby, Denmark (http://www.ie.dtu.dk) Tel.: +45 45 25 40 11 fax: +45 45 93 21 66 e-mail: pw@mek.dtu.dk Practical implications Supply air filters should be changed frequently not just because their airflow resistance increases progressively but because they degrade air quality with negative consequences for health, comfort and the performance of office work, all of which are factors that affect office productivity (profitability). Increasing outdoor air supply rates may only be beneficial when new filters are installed. Unwanted negative effects may be produced when used filters are in place. Filter condition (used or new) should always be recorded to make it possible to draw sound conclusions in studies of the effects of outdoor air supply rates on building occupants. Indoor Air 2004; 14 (Suppl 8): 7–16 www.blackwellpublishing.com/ina Printed in Denmark. All rights reserved Copyright Ó Blackwell Munksgaard 2004 INDOOR AIR 7