Physiological Responses to Elevated Carbon Dioxide Levels in Buildings

Abstract

Comparative tests were conducted involving 22 persons sleeping in a normal and in an elevated carbon dioxide (CO2) environment to determine respirato ry and urinary responses. Carbon dioxide levels in bedrooms with 2 occupants with the bedroom doors and windows closed can rise to 4,500 ppm during the night. The results indicate that the exposure levels encountered in these bedrooms do not affect the respiratory response, and that urine pH levels are independent of room CO2 levels, and somewhat dependent on diet. Since the buffering mechanism by the kidneys involves the release of phosphate for buffering, exposure to moderately elevated CO2 levels for several hours at a time may affect the excretion of phosphate and the metabolism of bone in the body. The literature indicates that persons exposed to 10,000 ppm over a peri od of several weeks experience a measurable bone loss. The threshold ambient level of CO2 at which this effect begins to take place and degree are not known.

Physiological responses during exposure to carbon dioxide and bioeffluents at levels typically occurring indoors

“…That no effects on respiration rate were seen is in agreement with the previous work by Stricker et al. (). They observed no effects on respiration rate when their subjects slept in a bedroom in which the CO 2 concentration was 3000 ppm throughout the night.…”

“…The indoor CO 2 concentration depends mainly on human occupancy (source strength) and on the outdoor air supply rate (dilution). They are typically below 2000–2500 ppm, but can reach as high as 4000–5000 ppm (e.g., Bekö et al., ; Menå and Larsen, ; Myhrvold et al., ; Shaughnessy et al., ; Stricker et al., ); that is, they can be up to one‐order of magnitude higher than outdoor levels, which are now on average about 400 ppm. Elevated CO 2 levels indoors are always accompanied by the other pollutants that are emitted either by humans (human bioeffluents) or by buildings.…”

Effects of exposure to carbon dioxide and bioeffluents on perceived air quality, self-assessed acute health symptoms, and cognitive performance

“…The concentration of CO 2 in buildings can be one order of magnitude higher than outdoors, typically being below 2000–2500 ppm, but in some cases reaching 4000–4500 ppm or even higher (e.g. Bekö et al., ; Menå and Larsen, ; Myhrvold et al., ; Shaughnessy et al., ; Stricker et al., ). A level of 5000 ppm is used as an occupational exposure limit for CO 2 (ACGIH, ), so levels of 5000 ppm and higher are expected to result in toxic effects, if exposure at this level is longer than 8 h and CO 2 is a dominant component of exposure.…”