Douglas VanOsdell

VOC Removal at Low Contaminant Concentrations Using Granular Activated Carbon

Small-scale beds of granular activated carbon (GAC) 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 GAC 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 degrees 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.

Growth evaluation of fungi (Penicillium and Aspergillus spp.) on ceiling tiles

The potential for fungal (Penicillium and Aspergillus spp.) growth on four different types of ceiling tiles was evaluated in static chambers. It was found that even new ceiling tiles could support fungal growth when at equilibrium with a relative humidity (RH) as low as 85% and corresponding moisture content (MC) greater than 2.2%. Used ceiling tiles appeared to be more susceptible to fungal growth than new ones. In the 70% RH chamber with wetted tiles under slow-drying, non-equilibrium conditions, fungi could still proliferate as long as the moisture level in the ceiling tiles was adequate. Fungal growth could be limited if the wetted ceiling tiles were dried quickly and thoroughly.

Assessment of fungal (Penicillium chrysogenum) growth on three HVAC duct materials

Abstract Many building investigators have documented fungal biocontamination in heating, ventilating, and air-conditioning (HVAC) ducts. It has been suggested that emissions of spores and volatile organic compounds from the growing fungi may contribute to poor indoor air quality and result in adverse health effects. Laboratory experiments were conducted to evaluate the susceptibility of three types of ventilation duct materials (fibrous glass ductboard, galvanized steel, and insulated flexible duct) to fungal ( P. chrysogenum ) growth. Each sample was inoculated with spores of P. chrysogenum and incubated in a static chamber controlled at 97% relative humidity (RH) and 21°C for six weeks. Culturable spores on each sample were enumerated before and after incubation to determine the extent of fungal amplification. The results indicated that, of the newly purchased duct materials, only the flexible duct supported moderate growth of P. chrysogenum . No fungal growth was detected on the fibrous glass and galvanized steel. The number of culturable spores on galvanized steel even decreased during the test period. Wetting the clean duct samples with sterile water did not increase amplification of the P. chrysogenum over the level seen without the wetting. Soiling the samples with dust collected from residential heating and air-conditioning systems enhanced the susceptibility of all three duct materials to fungal growth; however, at different levels of soiling. At a moderate level (0.4–0.7 mg cm −2 ) of soiling, growth occurred on the fibrous glass ductboard and the flexible duct, but not the galvanized steel. At a markedly higher level (9–18 mg cm −2 ) of soiling, growth was seen on the galvanized steel as well. The results of these experiments suggest that dust accumulation and/or high humidity should be properly controlled in any HVAC duct to prevent the growth of P. chrysogenum .

Experimental Study of Submicrometer and Ultrafine Particle Penetration and Pressure Drop for High Efficiency Filters

The fractional penetration of submicrometer particles through five high-efficiency glass fiber filters, one composite fiber filter, and two membrane filters was measured for particles of 0.004–0.42-μm diameter at filter face velocities ranging from 0.5 to 20 cm/s. The glass fiber filters all had approximately the same thickness and weight per unit area, and were rated 93% to 99.999% efficient using the conventional 0.3-μm dioctyl phthalate (DOP) test. The challenge aerosols were electrically classified monodisperse DOP in the diameter range of 0.032–0.42 μm, and polydisperse silver condensation aerosols having diameters of ∼ 0.004–0.01 μm. Aerosol penetration through these media was found to be generally consistent with current theory for collection by diffusion and interception over the particle size and velocity range studied. Using a filter figure of merit calculated for penetration by 0.1- and 0.3-μm particles to facilitate comparison, all of the filters except one tetrafluoroethylene membrane filter ...

Investigation of contact vacuuming for remediation of fungally contaminated duct materials

Environmental fungi become a potential Indoor Air Quality (IAQ) problem when adequate moisture and nutrients are present in building materials. Because of their potential to rapidly spread contamination throughout a building, ventilation system materials are of particular significance as potential microbial contamination sources. Current recommendations are to discard fibrous glass insulation that appears to be wet or moldy. Unfortunately, this advice is not always followed. Instead, cleaning is sometimes being used in buildings to remediate fibrous glass duct liner that is already contaminated with microbial growth. The objectives of this research program were to: 1) determine, under dynamic test conditions, whether fungal spore levels on heating, ventilating, and air-conditioning (HVAC) duct material surfaces could be substantially reduced by thorough vacuum cleaning, 2) evaluate whether subsequent fungal growth could be limited or contained by mechanical cleaning, and 3) provide data concerning the advisability of cleaning duct materials. The constant high relative humidity (RH) environment to which the test materials were exposed during this study was selected as a favorable growth environment that is frequently found in Southeastern United States HVAC systems. The results showed that, following cleaning, the levels of the two test fungi, A. versicolor and P. chrysogenum, recovered to preclean levels within 6 weeks. Therefore, mechanical cleaning by contact vacuuming alone was able to only temporarily reduce the surface fungal load. The current guidelines to discard contaminated materials should be followed.

Investigation of the Potential Antimicrobial Efficacy of Sealants Used in HVAC Systems

ABSTRACT Recent experiments confirm field experience that duct cleaning alone may not provide adequate protection from regrowth of fungal contamination on fiberglass duct liner (FGDL). Current recommendations for remediation of fungally contaminated fiberglass duct materials specify complete removal of the materials. But removal of contaminated materials can be extremely expensive. Therefore, a common practice in the duct-cleaning industry is the postcleaning use of antimicrobial surface coatings with the implication that they may contain or limit regrowth. Little information is available on the efficacy of these treatments. This paper describes a study to evaluate whether three commercially available antimicrobial coatings, placed on a cleaned surface that 1 year previously had been actively growing microorganisms, would be able to prevent regrowth. The three coatings contained different active antimicrobial compounds. All three of the coatings were designed for use on heating, ventilation, and air conditioning (HVAC) system components or interior surfaces of lined and unlined duct systems. Coating I was a polyacrylate copolymer containing zinc oxide and borates. Coating II was an acrylic coating containing decabromodiphenyl oxide and antimony trioxide. Coating III was an acrylic primer containing a phosphated quaternary amine complex. The study included field and laboratory assessments. The three treatments were evaluated in an uncontrolled field setting in an actual duct system. The laboratory study broadened the field study to include a range of humidities under controlled conditions. Both static and dynamic chamber laboratory experiments were performed. The results showed that two of the three antimicrobial coatings limited the regrowth of fungal contamination, at least in the short term (the 3-month time span of the study); the third did not. Before use in the field, testing of the efficacy of antimicrobial coatings under realistic use conditions is recommended because antimicrobials have different baseline activities and interact differently with the substrate that contains them and their local environment.

Building characterization and aerosol infiltration into a naturally ventilated three-story apartment building

Understanding infiltration of outdoor pollutants was an integral part of the Brooklyn Traffic Real-Time Ambient Pollutant Penetration and Environmental Dispersion (B-TRAPPED) study. For this reason, the structural and air exchange properties of the three-story row house in Brooklyn, NY, USA, that was used in the B-TRAPPED experiments were fully characterized. Factors investigated included representativeness of the construction and impact of building design features on the natural ventilation and infiltration of outdoor aerosol. Both blower door and perfluorocarbon tracer (PFT) air exchange rate (AER) experiments showed that the ventilation rates of the building were quite typical of similar structures in the New York City (NYC) metropolitan area. Indoor/outdoor (I/O) aerosol count ratios by particle size were comparable to a similar vintage naturally ventilated building in Boston, MA, USA. I/O ratio analyses were consistent with literature findings and showed I/O ratios ranging from 0.310 to 0.601, varying across particle sizes (from 0.3 to 5.0 [corrected] mum) and between first and second floor apartments. An effort to apply the rebound method of Thatcher et al. (Aerosol Sci. Technol., 2003, 37, 847-864) in determining aerosol infiltration rates proved unsuccessful due to unexpectedly long (>60 min) equilibration times after the filtration period. Uninsulated interior wall renovations in the study house created a cavity that resulted in a large intermediate dead volume (for infiltration) that apparently could not be accommodated by a simple infiltration model. Simple two-compartment models evidently have finite application limitations for even modestly complex settings.