Does control of indoor CO2 levels negatively impact IAQ?

C. O. Muller*, D. Bennett, Purafil, Inc., USA; R. McElligott, N. Glover, Future Decisions; P. Fish, Prisma Services Ltd., UK

Carbon dioxide (CO2) monitoring has long been used as a surrogate indicator of indoor air quality (IAQ). However, with the advent of multi-gas sensor technologies, this is a flawed and counterproductive approach in that low CO2 levels do not equate to good IAQ. A common misrepresentation of ASHRAE Standard 62.1: Ventilation for Acceptable Indoor Air Quality is that a target level of ~1,000 ppm for CO2 indicates acceptable IAQ. However, this does not necessarily guarantee good IAQ, and many believe this has detracted from addressing true causes of poor IAQ. ASHRAE even acknowledges such by removing the discussion of CO2 from normative sections of the standard. This has not kept CO2 out of the public eye with recent reports of productivity loss associated with raised levels. This information, along with current EU/UK building regulations detailing ventilation requirements, have led to a requirement for CO2 concentrations not to exceed ~1,200 ppm indoors, and leads to an assumption by design engineers that the now mandated CO2 measurement and abatement systems equate to better IAQ, and by proxy improved productivity. Applying a design approach to lower internal CO2 levels by increasing the intake rate of “fresh” outdoor air actually reduces IAQ in many locations. Within the built environment, this “fresh” air brings with it elevated levels of a range of pollutants including particulate matter, nitrogen dioxide, and ozone. Thus, higher ventilation rates increase indoor pollutant levels with a concurrent decline in IAQ. Results of investigations will be presented that show...

Session: G17 - HVAC-Systems
Day: 15 March 2018
Time: 14:45 - 16:00 h

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