No abstract

Small-scale beds of granular activated carbon (GAG) have been tested in this research using challenges of volatile organic compounds (VOCs) in air at concentrations ranging from approximately 0.5 to 100 ppm. The research linked the performance of GAG from high-concentration quickly completed tests to performance at low concentrations near those encountered indoors. For all tests, the carbon bed was approximately 2.54 cm thick and operated with a residence time of 0.11 s. The tests were conducted at 25 °C and 50% relative humidity.The measured 10% breakthrough times ranged from about 0.5 hour to several hundred hours. For the individual compounds, the relationship between the logarithms of breakthrough time and concentration was approximately linear over the experimental range, with different compounds producing lines having different slopes. The measured breakthrough times compared favorably to published data and models. The results suggest that higher-concentration single-component breakthrough tests, which are short and easily obtained, may be cautiously extrapolated to indoor concentrations for these compounds. IMPLICATIONSVolatile organic compounds (VOCs) have been identified as important contributors to poor indoor air quality (IAQ). Indoor VOC concentrations can be reduced through local control or source reduction, increased ventilation, and air cleaning. Beds of granular activated carbon (GAC) are the most commonly used air cleaning technology for VOCs at indoor concentrations. However, design and operating data at the low concentrations encountered indoors are scarce and difficult to obtain. Extrapolation of more available high-concentration performance data to indoor concentrations has not been demonstrated. These test results are directly applicable to constant, low-concentration challenge applications, and they support the use of conventional sorption models to predict performance at indoor concentrations.

No abstract

As attention has focused on indoor air quality, it has become important to obtain basic information on the effects of heating, ventilating, and air-conditioning system operating parameters on office aerosols. In addition, it is important to know the particle size distributions (PSDs) in a typical office environment in order to address mitigation strategies. Therefore, this study was undertaken to evaluate the effect of percent outdoor air supplied and occupation level on the PSDs and mass concentrations for a typical office building. The outdoor, return, and supply air streams, as well as hallway air, were sampled using measuring equipment covering particle diameters from below 0.1 to above 3.5 pm. The mass concentrations, when the building was occupied, increased by a factor of approximately 2 when return air was recycled over ventilating with maximum outdoor air. The concentrations when unoccupied were at least as low using minimum outdoor air as those when occupied using maximum outdoor air. As expected, the outdoor air was cleaner than the other streams. The next lowest concentrations were obtained for supply air, then return air, with hallway air showing the highest concentrations. The normalized number distributions were found to have a single mode consistently near 0.13 pm; the volumetric distributions show a peak at 0.3 pm. The influence of the damper setting and occupancy level shows up only in the magnitude of the peaks. The distributions found in the hall and for the air streams showed the same general shapes, but the differences in instrumentation preclude other conclusions.