Using Rn-222 to Manage the Air Quality of Air Conditioned Buildings in Hong Kong

This paper proposes a pragmatic methodology to manage the air quality of an air conditioned building as well as optimizing energy consumption during venting. Radon-222 (Rn-222) is used as a tracer to quantify the specific production rates and resultant losses of pollutants for which the information is important in indoor air quality management. A term, indoor pollutant inventory, is introduced for easy handling of various indoor pollutants. The specific production rate (Φ_j) of pollutant-j is the production rate of a pollutant normalized by the control volume of sampled room. The resultant loss (L _j)_RL of pollutant-j is defined as the sum of its natural decay (λ_j), reaction loss (R_j), and ventilation loss (q/v). Rn-222 and total volatile organic compounds are used to verify the methodology. In the verification tests, the air conditioned system of an office was scheduled to shut down overnight and return to supply mode in the next morning. The build-up and decay of the pollutants were measured and used to quantify (Φ_j) and (L_j)_RL. The values of (Φ_j) and (L_j)_RL obtained from the pollutants at two different modes mutually agreed with each other. The mean specific production rates of Rn-222 and TVOC were 20.7 Bq·m ^-3·h^-1 and 2.0 mg·m^-3·h^-1 respectively, while the lump sum of chemical and natural losses of these pollutants were 0.0076 h^-1 and 0.0226h^-1, respectively. Concentrations of the pollutants at various air change rates were also simulated in the study.