Modeling and monitoring of CO, NO and NO₂ in a modern townhouse

Mass-balance models for indoor concentrations of CO, NO and NO₂ were applied to an energy-efficient townhouse. Model parameters included source emission rates, infiltrating airflows, and, for NO₂, loss rate coefficients. Emission factors for CO, NO and NO₂ were estimated for each of the gas-fired appliances in the house. Airflows were estimated using sulfur hexafluoride (SF₆) decay techniques. Loss rates for NO₂ were calculated as the difference between NO₂ removal rates and estimated air exchange rates; CO and NO concentrations decayed at a rate not significantly different than that for SF₆. Comparing model predictions with measured concentrations yielded differences averaging 17% for CO and NO, and 28% for NO₂.