Serious research is being carried out at the university level to look at IAQ problems in sick buildings. Over the past eight years, Sidney Crow and his team of researchers at Georgia State University, Atlanta, have published a number of important papers on IAQ.

Crow’s research team includes microbiologists and organic chemists. They first identified the various types of mold, mildew, bacteria, and fungi that inhabit hvac systems, then went on to identify and quantify the various low molecular weight volatile organic compounds (VOCs) given off by the organisms.

Many of these VOCs are poisonous, and a number of them have potent smells. And this is why sick buildings stink: The microorganisms give off some terribly foul-smelling compounds.

Humid buildings

In one of his early papers, Crow teamed up with Charlene Bayer at Georgia Tech Research Institute. They visited nine buildings in the Atlanta area where there were occupant complaints about foul, musty odors.

These buildings included an Atlanta hotel, three public schools, two buildings on the campus of a Georgia university, a department store, a State of Georgia office building, and a residence.

In each building, the relative humidity was frequently above 70%.

Air sampling was performed to collect microorganisms on various types of growth media. Sampling was done in a way to measure the number of colony forming units (cfu) per cubic meter (cfu/cu m) of air.

Sampling was performed for the presence of VOCs, which were collected on multi sorbent tubes containing graphitized carbon blacks and glass beads.

Research results

A total of 145 samples was collected in the buildings and analyzed for fungi isolation and identification.

In addition, in two of the schools and the hotel, the VOCs were separated by gas chromatography and identified by mass spectroscopy, matching to a standard library of organic compounds.

Cultured organisms were grown for the purpose of collecting and characterizing the VOCs.

The highest population levels of fungi were detected in the residence. This house was supposed to have been built to minimize indoor contaminants. However, extremely high levels of cfu/cu m were found in the house.

The crawl space of this house was the apparent source, and the cfu’s seemed to migrate upstairs. In the basement, the concentration was over 10,500 cfu/cu m. In the other areas, levels ranged from 175 to 4,095 cfu/cu m.

Swab samples were taken in the dirty condensate pans in one of the schools. Some of the genera identified included Acremonium, Psudomas, Cladosporium, Xanthomas, and yeast.

The school had fibrous-lined return ducts that were excessively dirty. A swab sample taken in one of the cuts yielded moderate levels of Cladosporium, Aspergillus, Penicillium, Bacillus, and Microoccus varians.

In this school, the temperature at the time of the field survey was between 73° and 76°F, and humidity ranged between 56% and 58% rh. In all the schools, levels of fungi were higher in those areas of the building where there were complaints about air quality as opposed to other areas of the building.

In another school, there were 10 to 20 times higher cfu/cu m in the complaint areas than the non-complaint areas.

In almost every case where fungi were present, the major VOCs found were acetone, ethanol, and isopropanol. In certain instances, these compounds were such major components of the evolved gases that they overloaded the chromatographic systems in the instrumentation, and interfered with the detection of other VOCs.

The VOCs detected in the metabolic gaseous emissions of cultured fungi included several that are frequently identified in indoor environments.

Many of these VOCs are frequently theorized as originating from solvent-based materials and cleaning supplies. However, this is not the case, especially in the most badly contaminated buildings.

In the cultured fungi, the following VOCs were detected: methylene chloride, hexane, 2-heptanone, hexanol, 2-pentanol, methyl acetate, benzene, 2-propanyl acetate, acetone, carbon disulfide, 2-pentanone, furan, dihydrofuran, methyl furan, 2,2-dimethylpropanol, styrene, acetic acid, ethanol, isopropanol, 1,1-dimethyl hydroperoxide, ethyl acetate, 2-methyl-1-pripanol, 1,4-pentadiene, 1-methoxy-2-methylbenzene, and 3-methyl 2 butanone.

The compound 1-butoxy-2-propanol, a very foul smelling compound indeed, is often found in moldy areas of buildings. The compound 2-ethylhexanol is a known eye irritant with an unpleasant odor, and it may be associated with skin and upper respiratory irritations.

In the hotel and in two of the schools, the following compounds were identified as being present in the indoor air: acetone, benzene, 2-butoxyethanol, p-dichlorobenzene, 1,1dichloroethane, ethyl acetate, hexane, furan, limonene, pinene, tetrachloroethane, toluene, 1,1,1-trichloroethane, and xylene.

Hexane in a school

In one of the schools, there was a high level of hexane — more than 10 milligrams/cu m of air.

Hexane is a component of gasoline.

Since no other possible source of hexane could be found, it was determined to be due to the fungi that were clearly visible on the walls, carpets, fibrous duct lining, and in other areas of the building.

Some of the occupants of this building were suffering from sinusitis and severe asthma.

Penicillium was collected for study from each of the buildings. It gives off odors that are readily detectable in cultures. Moreover, Penicillia are commonly isolated in indoor air samples from many buildings.

The age of the Penicillium prior to collection impacted the detected gases. The alcohols, particularly ethanol and isopropanol, increase in concentration with the age of the culture broth.

The nutrient base, the site of fungal growth in the building, also appears to have an impact on the gas mixture. For example, Penicillium from the State of Georgia building emitted cyclic oxygenated compounds, such as dihydrofuran and tetrahydrofuran, while these compounds were not detected in the Penicillium from other buildings.

The Penicillium from the hotel emitted larger amounts of hexane than the other buildings.

In the examination of the 145 samples, one species, Cladosporium, was found in more than 50% of the samples that had fungi. Penicillium was the second most commonly found species.

In all of the samples, no more than five of the species of fungi were identified at any one place. This indicates relatively simple fungal ecosystems, with a small number of species.

An understanding of the production of metabolic gases from a relatively small number of fungi may clarify some of the sources of complaints in a building where there is no known cause, and may also pinpoint sources of airborne VOCs.

Research to be done involves identifying the evolved gases, understanding the age of the fungi as it affects the production of individual gases, and knowing how the nutrient base affects the formation of the gases.

Once knowledge is developed in these areas, the human response to fungi, even non-sporulating fungi, and the sources of complaints in buildings without obvious causes, can be better understood.