Indoor Air Facts No. 4 (revised) Sick Building Syndrome

United States Air and Radiation (6609J) Research and Development
Environmental Protection (MD-56)
Agency February 1991
Indoor Air Facts No. 4 (revised)
Sick Building Syndrome
The term “sick building syndrome” (SBS) is used to
describe situations in which building occupants
experience acute health and comfort effects that
appear to be linked to time spent in a building, but
no specific illness or cause can be identified. The
complaints may be localized in a particular room or
zone, or may be widespread throughout the
building. In contrast, the term “building related
illness” (BRI) is used when symptoms of
diagnosable illness are identified and can be
attributed directly to airborne building contaminants.
A 1984 World Health Organization Committee
report suggested that up to 30 percent of new and
remodeled buildings worldwide may be the subject
of excessive complaints related to indoor air quality
(IAQ). Often this condition is temporary, but some
buildings have long-term problems. Frequently,
problems result when a building is operated or
maintained in a manner that is inconsistent with its
original design or prescribed operating procedures.
Sometimes indoor air problems are a result of poor
building design or occupant activities.
Indicators of SBS include:
• Building occupants complain of symptoms
associated with acute discomfort, e.g.,
headache; eye, nose, or throat irritation; dry
cough; dry or itchy skin; dizziness and nausea;
difficulty in concentrating; fatigue; and
sensitivity to odors.
• The cause of the symptoms is not known.
• Most of the complainants report relief soon after
leaving the building.
Indicators of BRI include:
• Building occupants complain of symptoms such
as cough; chest tightness; fever, chills; and
muscle aches.
• The symptoms can be clinically defined and
have clearly identifiable causes.
• Complainants may require prolonged recovery
times after leaving the building.
It is important to note that complaints may result
from other causes. These may include an illness
contracted outside the building, acute sensitivity
(e.g., allergies), job related stress or dissatisfaction,
and other psychosocial factors. Nevertheless,
studies show that symptoms may be caused or
exacerbated by indoor air quality problems.
Causes of Sick Building Syndrome
The following have been cited causes of or
contributing factors to sick building syndrome:
Inadequate ventilation: In the early and mid
1900’s, building ventilation standards called for
approximately 15 cubic feet per minute (cfm) of
outside air for each building occupant, primarily to
dilute and remove body odors. As a result of the
1973 oil embargo, however, national energy
conservation measures called for a reduction in the
amount of outdoor air provided for ventilation to 5
cfm per occupant. In many cases these reduced
outdoor air ventilation rates were found to be
inadequate to maintain the health and comfort of
building occupants. Inadequate ventilation, which
may also occur if heating, ventilating, and air
conditioning (HVAC) systems do not effectively
distribute air to people in the building, is thought to
be an important factor in SBS. In an effort to
achieve acceptable IAQ while minimizing energy consumption, the American Society of Heating,
Refrigerating and Air-Conditioning Engineers
(ASHRAE) recently revised its ventilation standard
to provide a minimum of 15 cfm of outdoor air per
person (20 cfm/person in office spaces). Up to 60
cfm/person may be required in some spaces (such
as smoking lounges) depending on the activities
that normally occur in that space (see ASHRAE
Standard 62-1989).
Chemical contaminants from indoor sources:
Most indoor air pollution comes from sources inside
the building. For example, adhesives, carpeting,
upholstery, manufactured wood products, copy
machines, pesticides, and cleaning agents may
emit volatile organic compounds (VOCs), including
formaldehyde. Environmental tobacco smoke
contributes high levels of VOCs, other toxic
compounds, and respirable particulate matter.
Research shows that some VOCs can cause
chronic and acute health effects at high
concentrations, and some are known carcinogens.
Low to moderate levels of multiple VOCs may also
produce acute reactions. Combustion products
such as carbon monoxide, nitrogen dioxide, as well
as respirable particles, can come from unvented
kerosene and gas space heaters, woodstoves,
fireplaces and gas stoves.
Chemical contaminants from outdoor sources:
The outdoor air that enters a building can be a
source of indoor air pollution. For example,
pollutants from motor vehicle exhausts; plumbing
vents, and building exhausts (e.g., bathrooms and
kitchens) can enter the building through poorly
located air intake vents, windows, and other
openings. In addition, combustion products can
enter a building from a nearby garage.
Biological contaminants: Bacteria, molds, pollen,
and viruses are types of biological contaminants.
These contaminants may breed in stagnant water
that has accumulated in ducts, humidifiers and
drain pans, or where water has collected on ceiling
tiles, carpeting, or insulation. Sometimes insects or
bird droppings can be a source of biological
contaminants. Physical symptoms related to
biological contamination include cough, chest
tightness, fever, chills, muscle aches, and allergic
responses such as mucous membrane irritation
and upper respiratory congestion. One indoor
bacterium, Legionella, has caused both
Legionnaire’s Disease and Pontiac Fever.
These elements may act in combination, and may
supplement other complaints such as inadequate
temperature, humidity, or lighting. Even after a
building investigation, however, the specific causes
of the complaints may remain unknown.
A Word About Radon and Asbestos…
SBS and BRI are associated with acute or
immediate health problems; radon and asbestos
cause long-term diseases which occur years after
exposure, and are therefore not considered to be
among the causes of sick buildings. This is not to
say that the latter are not serious health risks; both
should be included in any comprehensive
evaluation of a building’s IAQ.
Building Investigation Procedures
The goal of a building investigation is to identify and
solve indoor air quality complaints in a way that
prevents them from recurring and which avoids the
creation of other problems. To achieve this goal, it
is necessary for the investigator(s) to discover
whether a complaint is actually related to indoor air
quality, identify the cause of the complaint, and
determine the most appropriate corrective actions.
An indoor air quality investigation procedure is
best characterized as a cycle of information
gathering, hypothesis formation, and hypothesis
testing. It generally begins with a walkthrough
inspection of the problem area to provide
information about the four basic factors that
influence indoor air quality:
• the occupants
• the HVAC system
• possible pollutant pathways
• possible contaminant sources.
Preparation for a walkthrough should include
documenting easily obtainable information about
the history of the building and of the complaints;
identifying known HVAC zones and complaint
areas; notifying occupants of the upcoming
investigation; and, identifying key individuals
needed for information and access. The
walkthrough itself entails visual inspection of critical
building areas and consultation with occupants and
staff. The initial walkthrough should allow the
investigator to develop some possible explanations
for the complaint. At this point, the investigator may
have sufficient information to formulate a
hypothesis, test the hypothesis, and see if the
problem is solved. If it is, steps should be taken to
ensure that it does not recur. However, if
insufficient information is obtained from the walk
through to construct a hypothesis, or if initial tests
fail to reveal the problem, the investigator should
move on to collect additional information to allow
formulation of additional hypotheses. The process
of formulating hypotheses, testing them, and
evaluating them continues until the problem is
Although air sampling for contaminants might
seem to be the logical response to occupant
complaints, it seldom provides information about
possible causes. While certain basic
measurements, e.g., temperature, relative humidity,
CO2, and air movement, can provide a useful
“snapshot” of current building conditions, sampling
for specific pollutant concentrations is often not
required to solve the problem and can even be
misleading. Contaminant concentration levels rarely
exceed existing standards and guidelines even
when occupants continue to report health
complaints. Air sampling should not be undertaken
until considerable information on the factors listed
above has been collected, and any sampling
strategy should be based on a comprehensive
understanding of how the building operates and the
nature of the complaints.
Solutions to Sick Building Syndrome
Solutions to sick building syndrome usually include
combinations of the following:
Pollutant source removal or modification is an
effective approach to resolving an IAQ problem
when sources are known and control is feasible.
Examples include routine maintenance of HVAC
systems, e.g., periodic cleaning or replacement of
filters; replacement of water-stained ceiling tile and
carpeting; institution of smoking restrictions; venting
contaminant source emissions to the outdoors;
storage and use of paints, adhesives, solvents, and
pesticides in well ventilated areas, and use of these
pollutant sources during periods of non-occupancy;
and allowing time for building materials in new or
remodeled areas to off-gas pollutants before
occupancy. Several of these options may be
exercised at one time.
Increasing ventilation rates and air distribution
often can be a cost effective means of reducing
indoor pollutant levels. HVAC systems should be
designed, at a minimum, to meet ventilation
standards in local building codes; however, many
systems are not operated or maintained to ensure
that these design ventilation rates are provided. In
many buildings, IAQ can be improved by operating
the HVAC system to at least its design standard,
and to ASHRAE Standard 62-1989 if possible.
When there are strong pollutant sources, local
exhaust ventilation may be appropriate to exhaust
contaminated air directly from the building. Local
exhaust ventilation is particularly recommended to
remove pollutants that accumulate in specific areas
such as rest rooms, copy rooms, and printing
facilities. (For a more detailed discussion of
ventilation, read Indoor Air Facts No. 3R,
Ventilation and Air Quality in Office Buildings.)
Air cleaning can be a useful adjunct to source
control and ventilation but has certain limitations.
Particle control devices such as the typical furnace
filter are inexpensive but do not effectively capture
small particles; high performance air filters capture
the smaller, respirable particles but are relatively
expensive to install and operate. Mechanical filters
do not remove gaseous pollutants. Some specific
gaseous pollutants may be removed by adsorbent
beds, but these devices can be expensive and
require frequent replacement of the adsorbent
material. In sum, air cleaners can be useful, but
have limited application.
Education and communication are important
elements in both remedial and preventive indoor air
quality management programs. When building
occupants, management, and maintenance
personnel fully communicate and understand the
causes and consequences of IAQ problems, they
can work more effectively together to prevent
problems from occurring, or to solve them if they

Indoor Air Facts No. 4 (revised) Sick Building Syndrome was last modified: May 31st, 2016 by Britt Bridges