A dynamic chamber (8 m3) was designed and constructed for the investigation of particulate emissions from appliances and office equipment and their impact on indoor air quality. The supply air incorporated high efficiency particle filters to provide a near-zero particle background in a low turbulence flow. The flow rate could be varied from 2 to 80 m3/min. For testing operating appliances, such as vacuum cleaners, the dimensions of the chamber were chosen to allow an operator to use an appliance over a floor area of about 2 m2. The need for low particle backgrounds dictated that the chamber be operated in an overpressure mode, so that all leaks were from the inside and would only affect the total flow measurements. The flow converges into an outlet tube 20 cm in diameter where velocity and concentration measurements could be made in multiple ports. The chamber was furnished with interior lights and electrical outlets.
Recently, the chamber has been modified with carbon filters on the inlet to allow for sampling of volatile organic compounds (VOCs), such as from floor wax. The filters remove the VOC background to a level below that detectable by the sorbent cartridges/analysis system used for sampling. The chamber has even been pressed into service as a small cleanroom for some operations that required its unique characteristics.
The chamber has been successfully operated in both a closed-loop mode and in an open loop mode. The main advantage of the closed loop mode is that the backgrounds can be reduced to zero more quickly, but the disadvantage is that humidity and carbon dioxide concentrations grow because they are not removed by the filters.
The chamber flow has been measured with helium trace gas with an interior stirring fan and been found to exhibit well-mixed decay characteristics, but when it is operated without the mixing fan, there are other tracer measurements that indicate a less-than-well-mixed flow. Chamber flow modeling is necessary to convert measured concentrations into source strengths, which are themselves usable in other indoor air quality models. Mathematical deconvolution of the time-dependent concentrations has also proved useful. Examples of vacuum cleaner and powder carpet cleaner emissions are presented to illustrate the types of emissions that can be measured in the chamber.