Models are an indispensable tool for predicting where and at what rate airborne pollutants will move throughout a building,
but they could not exist without measurements made in actual buildings. There is a wide array of building types, construction,
and ventilation systems (e.g. natural, forced, recirculating, etc.) which all influence pollutant movement within a building.
The APT group conducts field experiments that characterize airflow and pollutant transport under varying ventilation conditions
in buildings of different size, age, and construction type. The objectives of the field experiments include: 1) measuring the
air exchange rate between zones inside (e.g. rooms, floors, wings) and outside of buildings, 2) determining the rate of
mixing within and between zones, and 3) measuring flow rates of HVAC equipment. This information is critical to produce an
accurate and dependable predictive model.
A primary experimental method employed by the APT group to determine air exchange and mixing rates is tracer decay. An inert
tracer (typically sulfur hexafluoride or a perfluorocarbon) is released inside of a building. Measurements of the tracer
concentration are made with an array of monitors in different locations within the building, both during and after the release.
This data shows how pollutants move from one location to another under different building operating conditions.
Fan flow rates are determined using tracer released at a known constant rate upstream of the fan and measured downstream of the
fan. Penetration of outdoor pollutants can also be determined with an outdoor release and indoor measurements of a tracer or by
measuring the concentration of ambient contaminants within the building. For each building tested, these tracer experiments are
conducted for each of the building's ventilation operating conditions. The air exchange rate, fan flow rate, and penetration data
is then used to create and validate modeling simulation tools.
