June 29, 1999

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Resource: Thomas Sheldon June 29, 1999

Question: I am investigating some reported 'musty' smells in a hotel. The reports occur in guestrooms that have individual heating/cooling units and in an outside corridor. The building is about 20 years old and carpets about 10 years old. However, just to make sure I'm not missing anything, does anybody know of other non-fungal sources of musty smells that I should not discount at this stage?

Answer: As a self employed HVAC technician I have serviced many window units in homes and commercial settings. These are the usual jobs that most larger heating & air-conditioning companies will not touch. I found that neither home or business owner do any kind of general maintenance on such units. Therefore, over 90% of the room air-conditioners I come across are in need of some severe servicing. The large majority of complaints that I receive on these units is that the have begun to give off a very unpleasant odors or have stopped cooling efficiently. I've seen the evaporators in these units so chuck full of mold, dirt, tobacco resin and other unknown types of debris; it's a wonder how they were still running. Being that this building is twenty years old I would guess that the room air-conditioning systems are close to eight or more years old. These window units may be a very good source to check for odor problems being caused by lack of maintenance.

I would not at all be surprised if this was your major source of the complaint.

You've heard it many times: "My building stinks." And that's not figuratively, but literally.

This is not a joke.

You walk into a building, and you soon feel like you have a cold or the flu. This building is "sick," and it makes you sick. The facility has an affliction called Sick Building Syndrome. What you need to do is call in a "doctor" to cure the "patient"; in this case, the building.

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

Crow's interdisciplinary research team includes microbiologists and organic chemists. First the team identified the various types of mold, mildew, bacteria, and fungi that inhabit hvac systems. Then it identified and quantified 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 odors. So the reason sick buildings stink is because of the foul-smelling compounds given off by the microorganisms.

More Research

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

These buildings included a hotel, three public schools, two buildings on the campus of a Georgia university, a department store, a state office building, and a residence. In each building, the relative humidity was frequently above 70% rh.

Air sampling was performed to collect microorganisms on various types of growth media. Air sampling was done in a way to measure the number of colony-forming units per cubic meter (cfu/m3) of air, as well as for the presence of VOCs. VOCs were collected on multisorbent tubes containing graphitized carbon blacks and glass beads.

One-hundred and forty-five samples were collected 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.

Believe it or not, the highest population levels of fungi were detected in the residence. This house was supposed to have been built to minimize indoor con-tamination. However, extremely high levels of cfu/m3 were found. The crawl space was the apparent source, and the colony-forming units seemed to migrate upstairs. In the basement, the concentration was over 10,500 cfu/m3. In the other areas of the house, levels ranged from 175 to 4,095 cfu/m3.

Swab samples were taken from 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 the humidity ranged between 56% and 58% rh. In all the schools, the 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, the cfu/m3 were 10 to 20 times higher in the complaint areas than the non-complaint areas.

In almost every case where fungi were present in buildings, the major VOCs found were acetone, ethanol, and isopropanol. In certain instances, these compounds were such major components of the evolved gases that had developed 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 repiratory 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; 1,1-dichloroethane; 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/m3 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 said they had been 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 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.