Department of Civil and Environmental Engineering, Tufts University, Medford, MA 02155, USA.
Keck School of Medicine, Environmental Health Division, University of Southern California, Los Angeles, CA 90033, USA.
Sci Total Environ. 2018 Jan 1;610-611:1448-1456. doi: 10.1016/j.scitotenv.2017.08.105. Epub 2017 Sep 1.
Limiting the air exchange of passenger vehicles by closing windows and recirculating cabin air (RC) restricts the influx of roadway pollutants and reduces in-vehicle particulate concentrations. However, the carbon dioxide (CO) exhaled by the occupants can accumulate under these conditions to reach high concentrations. We characterized the factors (ventilation setting, vehicle age, speed, cabin volume, trip duration, and number of occupants) that allow CO accumulation to reach concentration thresholds found in other studies to produce cognitive or physiological effects of concern such as fatigue or difficulty concentrating. Ventilation setting was the primary determinant of CO accumulation; only the RC setting (and not outside-air intake) ever allows CO accumulations to exceed thresholds of concern. Longer trips with multiple occupants are a particular concern. Even so, under RC setting, a 2500ppm threshold-the threshold consistently linked to detrimental cognitive effects-would not be exceeded for most one- or even two-occupant average-duration commutes (twenty-six minutes in the U.S.). For multiple passenger commutes and/or longer trips, RC ventilation should be periodically interrupted or partially mixed with outside air to keep CO concentrations below 2500ppm.
通过关闭车窗和循环车内空气（RC）来限制乘用车的空气交换，可限制道路污染物的涌入并降低车内颗粒物浓度。然而，在这种情况下，乘客呼出的二氧化碳（CO）会积聚，达到很高的浓度。我们研究了使 CO 积聚达到其他研究中发现的浓度阈值的因素（通风设置、车辆年龄、速度、车厢体积、行程持续时间和乘客数量），这些阈值可能会产生认知或生理影响，例如疲劳或注意力难以集中。通风设置是 CO 积聚的主要决定因素；只有 RC 设置（而不是外部空气进气口）会导致 CO 积聚超过关注的阈值。有多个乘客的长途旅行尤其令人担忧。即便如此，在 RC 设置下，大多数单人或甚至两人平均行程（美国为 26 分钟）的 2500ppm 阈值（与认知损害效应一致的阈值）不会被超过。对于多乘客通勤和/或长途旅行，RC 通风应定期中断或部分与外部空气混合，以将 CO 浓度保持在 2500ppm 以下。
