John C.S. Chang

Review of Quantitative Standards and Guidelines for Fungi in Indoor Air

Existing quantitative standards/guidelines for fungi in indoor air issued by governmental agencies are based primarily on baseline data (rather than health effects data), and are either absolute (numerical) or relative (indoor/outdoor comparisons) or a combination of the two. The Russian Federation is the only governmental agency that has binding quantitative regulations for bioaerosols. Recommended guidelines have been proposed or sponsored by North American and European governmental agencies and private professional organizations. A considerable number of frequently cited guidelines have been proposed by individuals based either on baseline data or on personal experience. Quantitative standards/guidelines range from less than 100 CFU/m3 to greater than 1000 CFU/m3 (total fungi) as the upper limit for non-contaminated indoor environments. Major issues with existing quantitative standards and guidelines are the lack of connection to human dose/response data, reliance on short term grab samples analyzed only by culture, and the absence of standardized protocols for data collection, analysis, and interpretation. Urgent research needs include the study of human responses to specific fungal agents, development and widespread use of standard protocols using currently available sampling methodologies, and the development of long term, time-discriminating personal samplers that are inexpensive, easy to use, and amenable to straightforward, relevant analysis.

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 .

Predicting the emissions of individual VOCs from petroleum-based indoor coatings

The indoor use of petroleum-based coating materials may cause elevated volatile organic compound (VOC) concentrations. This paper presents a newly developed mass transfer model for estimating the emissions of individual VOCs from freshly coated surfaces. Results of a four-step validation show that the predicted individual VOC emissions are in good agreement with experimental data generated in small chambers and an indoor air quality test house. The values of the parameters introduced in this model are all easily obtained, and thus its utilization can provide indoor air quality professionals with emission rate estimates for individual VOCs without having to conduct costly dynamic chamber testing.

Estimation of the rate of VOC emissions from solvent-based indoor coating materials based on product formulation

Abstract Two computational methods are proposed for estimation of the emission rate of volatile organic compounds (VOCs) from solvent-based indoor coating materials based on the knowledge of product formulation. The first method utilizes two previously developed mass transfer models with two key parameters – the total vapor pressure and the average molecular weight for total volatile organic compounds (TVOCs) – being estimated based on the VOC contents in the product. The second method is based on a simple, first-order decay model with its parameters being estimated from the properties of both the source and the environment. All the model parameters can be readily obtained. Detailed procedures for computing the key parameters are described by using examples. The predictive errors were evaluated with small chamber data, and the results were satisfactory. Thus, the proposed methods provide a way to predict the VOC emissions in the indoor environment without having to conduct costly chamber testing. The two proposed methods work for both TVOCs and individual VOCs. Pros and cons for each method are discussed.

Emissions of odorous aldehydes from alkyd paint

Abstract Aldehyde emissions are widely held responsible for the acrid after-odor of drying alkyd-based paint films. The aldehyde emissions from three different alkyd paints were measured in small environ-mental chambers. It was found that, for each gram of alkyd paint applied, more than 2 mg of aldehydes (mainly hexanal) were emitted during the curing (drying) period. Since no measurable hexanal was found in the original paint, it is suspected that the aldehydes emitted were produced by autoxidation of the unsaturated fatty acid esters in the alkyd resins. The hexanal emission rate was simulated by a model assuming that the autoxidation process was controlled by a consecutive first-order reaction mechanism. Using the emission rate model, indoor air quality simulation indicated that the hexanal emissions can result in prolonged (several days) exposure risk to occupants. The occupant exposure to aldehydes emitted from alkyd paint also could cause sensory irritation and other health concerns.

Modeling of the fast organic emissions from a wood-finishing product—Floor wax

Abstract Environmental chamber and full-scale residential house tests were conducted to evaluate the fast organic emissions from a wood-finishing product—floor wax. For the environmental chamber tests, a very small amount of ( −2 ) of the wax was applied to an aluminum plate. It was found that the chamber exit organic concentrations can be estimated by a model with an initial condition of instant organic emissions. The model was applied to the house data to interpret the octane and nonane emissions. Significant sink effects were found in the house that prolonged the elevated octane and nonane concentrations for more than 2 days.