“Musty,”
“mildew,” “moldy,” “earthy,” “dirty socks,” “gym
locker,” “rotten egg,” “foul,” “sour milk,”
“garbage,” “sewage,” “fishy,” “something dead,”
“chemical,” are all common descriptions of
unpleasant odors that most people find disturbing or
distracting.
People affected seldom
care about the source or cause of the odor;
they just want it to go away. Not many firms
actually specialize in investigating odor
problems. There are no “magic sniffers” that
can either determine the constituents, the
source or the cause of an odor. It appears
to be the case that the best tool still in
tracking down an odor is the trained and
sensitive nose. Add to this tool a thorough
knowledge of a wide variety of odor causes
plus factors and driving forces affecting
air pathways. With this specialized
knowledge and the common tool (nose) along
with chemical smoke tubes, the causes and
sources of odor problems can be located and
guidance can be provided on steps to take to
eliminate them. The purpose of the chemical
smoke is to determine pressure relationships
when the odor is present for the purpose of
tracking it back to its source.
The odor investigator’s job is to determine
why the odor is in the location where people
are complaining, where it comes from and how
to eliminate it. Often the odor is
intermittent; it comes and goes. Changing
pressure relationships within a building can
cause air to flow from unoccupied regions
where unpleasant odors are expected into
occupied spaces where they are not supposed
to be. These unoccupied regions can be such
areas as attics, basements, wall interiors
and other cavities. Occupied locations where
odors might be expected can also become
offending odor sources when these odors are
not properly contained or exhausted. These
areas include restrooms, kitchens and break
rooms. Work areas that produce odors as a
matter of course must also be properly
contained or exhausted so as not to let
odors migrate to areas where they don’t
belong. The most effective way we know of
solving intermittent odor problems is to
investigate the problem when the odor is
present in areas where it is in not expected
or wanted. Once the odor has been positively
identified and is present, locating the
source consists of generally just following
it back to the source.
Often even locating the source for an odor
when it is present is not necessarily a
simple process. In one case personnel in one
office building complained of an
intermittent sewer odor that occurred in
several building locations. Part of the
problem with locating the source was that
the ventilation systems were fan/coil units
located above the ceiling. This was an open
ceiling return so the air above the
ceiling was shared by
numerous fan/coil units. Using ladders to
access above the ceiling we were finally
able to trace the odor back to its source
partially by finding the general area where
the odor appeared to be strongest. But even
this tracing of the odor was not sufficient
to locate the source quickly. One piece of
information enabled us to find the offending
location more quickly. Speaking with one of
the management personnel we discovered that
the odor had been present to some degree
ever since the company had occupied the
building. It was also stated that the build
out prior to occupation was done quickly due
to a tight deadline. We also learned that
some restrooms had been moved and offices
put in their place. With that information we
were able to locate a sewer vent pipe inside
a wall that had not been capped when the
restroom was moved. Once that was found and
the pipe properly capped, the odor problem
was solved.
The most difficult assignment for an
investigator is to determine the source of
an odor that is not there at the time of the
investigation and where no positive
identification has been made. There have
been times when we have been able to find an
odor source without the smell being present.
An accurate description of the odor plus the
conditions surrounding the times the odor
has been present is sometimes sufficient to
locate the source. One problem with locating
odors using this method is that odors are
sometimes subjective and difficult to
describe. This is essentially using a theory
system for determining the odor source. This
system is often difficult and time
consuming. It requires experience in
detecting odor sources as well as knowledge
of air pathways in buildings. It may require
having personnel on site keeping a log of
when the odor is present in particular
locations and the duration. Such logs can
enable an investigator to trace to the
source by determining where it first occurs
and to what locations it travels.
While difficult to locate the source of an
odor by the theory method, sometimes general
knowledge coupled with a bit of intuition
can produce dramatic results. Such was the
case with a company that produced precision
electronic products in clean rooms. Over a
period of months at various times some of
the clean rooms had to be evacuated due to a
very unpleasant odor whose source could not
be identified. The company had spent
thousands on various professionals
attempting to locate the odor source, to no
avail. Having heard that our company
specialized in odor investigations, we were
called in to solve the problem. The
principals of the company concerned did not
have a lot of confidence in our being able
to solve the problem after all the other
failures. According to the information
provided, we suspected that the source of
the odor was related to the HVAC system
serving the area. It was a big package unit
with the main supply duct so large we could
stand up in it. We noticed that the unit was
equipped with a humidifier that was used
primarily to keep the incidence of static
electricity low. We had the humidifier
activated as an experiment. After the
humidifier came on we left the HVAC system
in order to observe any effect in one of the
clean rooms. Before we could get to our
destination, the clean room was already
being evacuated due to the odor. Upon
questioning, we discovered that the
humidifiers were provided with water from a
large water storage container. Further
questioning revealed that the anti-scaling
chemicals used in the storage container had
been changed to another brand just prior to
the odor complaints. Once the chemicals were
changed back to those previously used, the
odor problem disappeared. After the company
spending thousands of dollars attempting to
solve the problem in addition to many man
hours of lost production, we had discovered
the source of the odor in less than an hour.
We were the heroes of the day. Knowledge and
intuition are great tools, but being lucky
enough to find it with the first action
taken makes you look like miracle workers.
There is a common odor phenomenon that
occurs due to microbially contaminated
cooling coils in an air conditioning system.
This odor situation reportedly is most
prevalent with heat pump systems. This is
usually bacterial and sometimes fungal
contamination resulting in an odor situation
known as “Dirty Socks Syndrome.” It may
actually be intermittent in that it is only
noticeable when the coil becomes wet enough
to activate the bacteria. The odor is
generally described as smelling like a gym
locker or dirty socks, hence the name of
this phenomenon. Swab sampling of the coil
can confirm the condition with bacterial
analysis. High bacterial levels usually
signal that you have found the source of the
odor. The solution to “Dirty Socks” is to
pressure wash the coil thereby removing all
the nutrients supporting microbial growth
and then sanitizing the coil to kill the
microbes.
Sewer odors are quite common complaints.
Broken or cracked sewer vent pipes inside
walls or above ceilings can result in
intermittent sewer odors that can be very
frustrating in trying to locate the source.
Most common is having sewer odors pulled
into the HVAC system through the outside air
(OSA) inlet. This is usually a design
problem whereby sewer vent pipes exit too
close (within 15 feet or so) of the outside
air inlet of the HVAC system. Sometimes even
with vent pipes far away from the OSA inlet,
sewer odors can still be pulled into the
indoor air via the air conditioning system
with certain wind speeds and direction. If
the vent pipe is upwind and/or lower on the
roof than the outside air inlet, the odor
can be carried across the roof to be picked
up at the OSA inlet. It is often necessary
to use PVC pipe to extend the vent pipe
outlet to six feet or so above the roofline
enabling the odor to be dissipated by the
wind.
Insufficient HVAC outside air can exacerbate
virtually any odor generated indoors
allowing it to build up with too little
outside air to dilute it. Conversely,
sufficient outside air can mitigate such
odors. This rule, of course, assumes that
the source of the odor is indeed inside and
not being provided by the HVAC system via
microbially contaminated coils or through
the OSA inlet. We have known cases where
outside air inlets were closed off to
eliminate odors from outdoors. Much of the
time they are closed off due to sewer odors
being pulled into the system or because of
odors generated by re-roofing nearby.
Certainly there may be valid reasons for
closing off outside air inlets for short
periods of time due to acute periods of
outdoor odors, but failure to supply
sufficient outside air on any continuous
basis is just asking for odor and potential
health problems down the line.
In summary, odor investigations can be quite
difficult even for professionals. The first
step is to identify the odor as nearly as
possible. Try to relate it to something you
have experienced before so you have a method
of describing it. Keep in mind that odors do
tend to change a bit as they move farther
and farther from the source. An odor that
originates on the first floor of a building
may still be unpleasant but substantially
different by the time it reaches the third
floor.
If you are unable to locate the source
yourself, there are people you can call to
assist, such as plumbers or HVAC
contractors. Companies that specialize in
odor problems are relatively rare, but if
you find one with knowledgeable and
experienced investigators, it is often most
cost effective to contact them first so the
odors can be quickly eliminated and
personnel can get back to production without
the distraction of unpleasant odors
competing for their attention.
