Effect of room air recirculation delay on the decay rate of tracer gas concentration

Tracer gas measurements are commonly used to estimate the fresh air exchange rate in a room or building. Published tracer decay methods account for fresh air supply, infiltration, and leaks in ductwork. However, the time delay associated with a ventilation system recirculating tracer back to the room also affects the decay rate. We present an analytical study of tracer gas decay in a well-mixed, mechanically-ventilated room with recirculation.

Simple and Cheap Air Change Rate Measurement Using CO2 Concentration Decays

Buildings are aired to evacuate indoor pollutants, in particular those produced by the occupants. CO2 is a good indicator of occupancy, as long as there is no other significant source. This is the case in most buildings. Cheap, portable analysers and loggers that allow easy recording of the CO2 concentration in a room or in the exhaust duct of a ventilation system are available on the market. The peak value of CO2 concentration during occupancy is an indicator of the minimum air flow rate per person.

Standard test method for determining air leakage rate by tracer dilution.

This test method describes a standardized technique for determining air change rate in buildings under natural meteorological conditions by trace gas dilution

The use of detector tubes with carbon dioxide as a tracer gas.

Tracer gas concentrations are often analysed by using infrared spectroscopy. Infrared gas analysers have a fast response time and are accurate. Howener, this type of instrumentation is relatively expensive and can only be used for this type

Measured ventilation and infiltration rates in eight US government office buildings.

Ventilation and infiltration rates were measured in eight office buildings using an automated tracer-gas measurement system. The buildings range in size from a two-story building with a floor area of about 2000 m2 to a 15-story office building.