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.