Occupant-generated CO2 as an indicator of ventilation rate.

Reports on 2 methods of measuring ventilation rates in the 8-storey San Francisco Social Services Building, using occupant-generated CO2 as a tracer gas. Measures CO2 concentration at regular intervals on the first floor using an infra-red gas detector. Uses the tracer gas decay method and the constant concentration (integral) method to determine ventilation rates. Finds that the CO2 decay method compares favourably with both SF6 tracer gas measurements and with air-flow measurements in the ducts. The integral method of determining ventilation rate is satisfactory when the system is circulating outside air, but it overestimates the ventilation rate when air is recirculated, because of the presence of CO2 gradients. When outside air ventilation rates are low, CO2 concentration rises and the CO2 decay method is more easily applied.