Occupant symptoms are the primary means by which a building operator usually becomes aware of IAQ problems in the building. These often begin as innocent complaints and can escalate to the point where extremely damaging publicity, occupant lawsuits, and even evacuation of buildings can occur. The primary focus of this article will explore symptoms commonly associated with IAQ problems in buildings, as well as their likely sources of contamination. Additionally, the role of biological contaminants has been of growing concern as compared to the traditional nonbiological contaminants, such as organic chemicals, particulate matter, and toxic gases, which have been previously recognized as primary concerns.

Varying degrees of severity

From a clinical perspective, occupant symptom complaints frequently vary significantly in degree of severity. The occupant symptoms generally fall into three basic categories: odors, Sick Building Syndrome (SBS), and Building-Related Illness (BRI).

Typically, nuisance odors have minimal health impact when compared to other occupant complaints, although they may serve as important warning signals of an imminent IAQ problem.

Examples include sewage-like odors which can result from re-entrainment of toilet exhaust at rooftop levels, garbage odors from dumpsters placed too close to outside air intakes, cooking odors from cafeterias and restaurants in which odors are not properly exhausted from the building, and body odors from lack of outside dilution ventilation. Often building managers can address these problems in their early stages by carefully listening to the complaint and then diagnosing the cause of it.

Nuisance odors should always be addressed seriously and never casually dismissed. To do so can irreparably damage the credibility of the building manager and, at the same time, the building manager may lose a valuable opportunity to correct a minor problem before it escalates to a serious magnitude.

For the person experiencing nuisance odors, such odors can be extremely unpleasant. Some municipalities in California have gone so far as to create "fragrance free" buildings in recognition that certain colognes and perfumes can be nuisances. It is interesting to note that in contrast to the manner in which U.S. ventilation standards are set for occupant comfort, most European standards are designed to safeguard against the perception of offensive human body odors.

SBS is probably the most common complaint that our company encounters. SBS, as its name implies, is a conglomeration of similar symptoms that cannot necessarily be attributed to any particular disease. Examples include headaches; burning eyes, nose, and throat; nausea; skin rashes; coughing; sneezing; and fatigue. Because these symptoms can be attributable to a variety of different causes - many of which are unrelated to occupancy in the building - for the building investigator, the key clue is the pattern of the symptoms as they occur.

Typical SBS symptoms may occur from a few minutes to a few hours after entering a building and tend to get progressively worse throughout the day. By day's end, the SBS sufferer can be almost totally debilitated, and upon leaving the building, symptoms mitigate slightly-to-completely in a matter of minutes-to-hours. This pattern is repeated until the sufferer eventually concludes that the building is the cause of the symptoms.

It is important to recognize SBS symptoms as soon as possible and to investigate their causes because, if left untreated, many experts believe that SBS symptoms may eventually lead to BRI. In theory, SBS symptoms are the initial indicator of damage to the immune system, nervous system, etc., and that prolonged insult to the body's systems can lead to disease conditions.

The beginning of disease

The most severe category of occupant complaints is BRI. These are clinically diagnosable diseases where a physician can perform a test or conduct an examination and conclusively diagnose the disease as having an environmental cause and, in all likelihood, will associate the building with the onset of the disease.

The following is a discussion of a number of the most common BRIs, but this list should not be considered exhaustive.


Fungal (mold)-related diseases are the most common diseases that our company observes in building occupants. Allergies are an immune system overreaction to exposure to environmental contaminants, such as mold. The typical response is that the body overproduces immunoglobulins and triggers the release of a chemical called histamine, which causes nasal swelling and congestion. While mold allergies are common, there are other allergens commonly found in a building that can also trigger allergic responses, such as cat and dog dander, cockroach antigens, dust mite feces, and pollen.


Asthma is a hypersensitivity response which may be triggered by exposure to a wide range of environmental stimuli, including molds, tobacco smoke, carbon-based particulates, and many others. Asthma is a restrictive airway disease that can be fatal. There are also nonenvironmental triggers, such as stress and exercise.


Infections can be caused by all major categories of biological contaminants, including viruses, fungi, and bacteria. Viruses are nonliving pieces of DNA or RNA genetic material that are capable of commandeering the body's cells for purposes of reproduction of the viral genetic material. Viruses are very aggressive and can overrun a body's defense mechanisms in a very short period of time, thus giving rise to fevers, chills, and nausea, sometimes in a matter of hours. At present, there is no practical method for measuring viral particles in the air, but it is generally accepted that a single cough or sneeze can liberate literally millions of viral particles into the air if an individual is infected.


Gram-negative bacteria are a major category of the infectious agents that can cause a variety of diseases including Legionnaire's disease and Pontiac Fever. Other opportunistic gram-negative pathogens such as Pseudomonas species, Flavobacterium sp, and Burkholderia cepacia, may also colonize a host and promote subsequent infection. These gram-negative bacteria are commonly found in contaminated air and water, which causes respiratory, kidney, lung, and bacteremia infections.


While airborne fungal infections are probably the least common type of infection encountered by building occupants, it is not unusual that individuals can develop eye, ear, nasal, and upper respiratory infections which can be life-threatening. For example, the fungus Aspergillus fumigatus is a highly opportunistic pathogen that is capable of causing a persistent lower respiratory infection which can be life-threatening for those who are immunocompromised.

Outbreaks of aspergillosis occurring in hospital settings are viewed with extreme concern. Contamination sources can include colonized building materials, such as drywall and ceiling tiles, or water sources, such as pools, hot tubs, and humidifiers. Another fungi of special concern is Aspergillus flavus, especially strains that produce chemical metabolites (aflatoxins), which have been recognized as potent carcinogens.

It is commonly accepted among medical professionals that most infections are transmitted through direct person-to-person contact or contact with contaminated environmental surfaces, although research has demonstrated in numerous instances that exposure and subsequent infection may occur readily through the inhalation route as well. Further investigation is greatly needed in this area.

Dermal irritancy

Skin rashes (erythemia) are a common symptom in building occupants where microbial contamination is present. For example, people exposed to Stachybotrys chartarum frequently suffer bright red rashes as a result of contact with this organism. It is unclear whether such skin rashes are infections or toxic or allergic responses.

Toxic responses

Current media attention has focused largely on responses caused by exposure to toxigenic ("poison-producing") molds. The majority of attention has been focused on the organism Stachybotrys chartarum, which appears to be capable of producing up to eight different mycotoxins which may have bizarre and profound effects on exposed occupants.

The focus on this organism in building settings occurred in 1994 when a number of infants in the Cleveland area developed respiratory symptoms which were initially attributed to exposure to this organism, and many other children suffered symptoms which made them extremely ill. The conclusions of the investigation into this outbreak have recently come into question, however, and many experts believe that there was a direct cause-and-effect relationship in this outbreak and in many others that have occurred throughout the country.

Under appropriate environmental conditions, Stachybotrys chartarum may produce potent toxic compounds that influence the health of those exposed in various ways. While the infants in Cleveland ultimately died from a condition called pulmonary hemosiderosis in which they bled from their nose and mouth, adults appear to have different sets of symptoms including inability to fight off infections, personality changes, and short-term memory loss. Additional research is revealing that many molds are capable of producing mycotoxins and that other species may be as great a threat as Stachybotrys chartarum.

Endotoxins are compounds produced by gram-negative bacterial cell walls and are believed to play an important role in the development of organic dust-related diseases in exposed workers. High levels are found in varied environments, such as cotton mills, agricultural workplaces, biosludge plants, machining operations, laboratories, homes, hospitals, and swimming pools. The highest reported levels are associated with wastewater treatment and recirculating industrial wastewater spray. Endotoxins are also found in the mist of ultrasonic and cool-mist humidifiers.

Exposure to concentrations of airborne endotoxins (>20 eµ/m3) can cause acute fever, lung-function alterations, respiratory complaints (chest tightness, cough, shortness of breath, and wheezing), mucosal irritation, dry throat, skin irritation, and rashes.


BRIs and SBS symptoms can result from literally thousands of causes. The majority of these are of biological origin and can be controlled by identifying sources and correcting the conditions which favor growth of these organisms. The building engineer has, in addition to source removal, the additional tools of increasing dilution ventilation and improving air filtration if total contaminant source control or elimination cannot be achieved.