"Musty" Smells in Hotel Rooms
June 29, 1999
BBJ MicroBiocide, the only EPA registered product specifically
for HVAC systems, is highly effective in preventing or inhibiting
the growth of active microorganisms such as bacteria, algae,
mold and other fungi that grow in heating, ventilation and
air-conditioning ("HVAC") systems for months at
a time. Although BBJ MicroBiocide effectively kills these
microorganisms upon application, what makes this product
unique is its ability to make that same treated surface
uninhabitable to future microbial growth for months at a
time. As Dr. Yang reported in his article entitled Biological
Contamination in the HVAC System, by preventing the growth
and establishment of colonies, you effectively eliminate
the various health effects caused by microbes in the HVAC
system; and BBJ MicroBiocide is the only EPA registered
product that will prevent the growth and establishment of
colonies for months at a time.
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
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%
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
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
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
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