Carbon dioxide (CO2) levels are often measured during the course of an indoor air quality investigation. The CO2 level is an easy to measure indicator of the general effectiveness of a ventilation system. ASHRAE Standard 62.1 suggests that indoor CO2 levels of 700 parts per million (ppm) or less above the measured outside air level are indicative of a ventilation system that is providing an amount of outside air sufficient to control bioeffluents and odors within the space. The OSHA Permissible Exposure Limit for CO2 is 5000 ppm for an 8 hour Time Weighted Average exposure. Serious health effects from an elevated carbon dioxide exposure would not be expected to appear until levels exceed 15,000 ppm.
It is important to remember that there currently are no regulatory limits regarding mold levels in an indoor environment and that the permissible exposure limits (PEL) for chemical contaminants mandated by OSHA are generally applicable to an industrial setting rather than to an office or classroom environment.
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