Respiratory performance of humans exposed to moderate levels of carbon dioxide.

In a business as usual scenario, atmospheric carbon dioxide concentration (CO ₂ ) could reach 950 parts per million (ppm) by 2100. Indoor CO ₂ concentrations will rise consequently, given its dependence on atmospheric CO ₂ levels. If buildings are ventilated following current standards in 2100, indoor CO ₂ concentration could be over 1300 ppm, depending on specific ventilation codes. Such exposure to CO ₂ could have physiological and psychological effects on building occupants. We conducted a randomized, within-subject study, examining the physiological effects on the respiratory functions of 15 persons. We examined three exposures, each 150 min long, with CO ₂ of: 900 ppm (reference), 1450 ppm (decreased ventilation), and 1450 ppm (reference condition with added pure CO ₂ ). We measured respiratory parameters with capnometry and forced vital capacity (FVC) tests. End-tidal CO ₂ and respiration rates did not significantly differ across the three exposures. Parameters measured using FVC decreased significantly from the start to the end of exposure only at the reduced ventilation condition (p < 0.04, large effect size). Hence, poor ventilation likely affects respiratory parameters. This effect is probably not caused by increased CO ₂ alone and rather by other pollutants-predominantly human bioeffluents in this work-whose concentrations increased as a result.
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