Handbook of air conditioning and refrigeration / Shan K

4.10 SICK BUILDING SYNDROME AND INDOOR AIR QUALITY
Indoor Air Contaminants
INDOOR AND OUTDOOR DESIGN CONDITIONS 4.27
Sick building syndrome is a kind of building-related illness that has received public attention since
the 1970s. ASHRAE (1987) defined the sick building as “. ..a building in which a significant
number (more than 20 percent) of building occupants report illness perceived as being building related.
This phenomenon, also known as ‘sick building syndrome’ is characterized by a range of
symptoms including, but not limited to, eye, nose, and throat irritation, dryness of mucous membranes
and skin, nose bleeds, skin rash, mental fatigue, headache, cough, hoarseness, wheezing,
nausea, and dizziness. Within a given building, there usually will be some commonality among the
symptoms manifested as well as temporal association between occupancy in the building and appearance
of symptoms.” If there are signs of actual illnesses, these illness are classified as buildingrelated
illnesses.
Poor indoor air quality (IAQ) is the dominant factor that causes sick building syndrome. Indoor
air quality is defined as an indication of harmful concentrations of the indoor air contaminants that
affect the health of the occupants or the degree of satisfaction of a substantial majority (80 percent
or more) of occupants exposed to such an indoor environment. Poor control of the indoor air temperature
and relative humidity are causes of discomfort symptoms. They may also increase the
indoor air contaminants. However, unsatisfactory indoor temperature and indoor relative humidity
are only indirect causes of poor indoor air quality.
National Institute for Occupational Safety and Health (NIOSH) of the United States (1989),
according to the results of 529 building investigations between 1971 and 1988, and Health and
Welfare Canada (HWC), according to the results of 1362 building investigations between 1984
and 1989, classified the reasons for sick building syndrome as follows:
NIOSH, 529 Buildings HWC, 1362 Buildings
No. of buildings Percent No. of buildings Percent
Inadequate ventilation 280 53 710 52
Indoor contaminants 80 15 165 12
Outdoor contaminants 53 10 125 9
Biological contaminant 27 5 6 0.4
Building fabric contamination 21 4 27 2
Unknown sources 68 13 329 24
Inadequate ventilation includes lack of outdoor air, poor air distribution, poor thermal control, and
inadequate maintenance; and it is the primary cause of indoor air quality. The survey found 70 to 80
percent of the investigated buildings had no known problems. Effective operation and control of the
HVAC&R system will be discussed in later chapters.
In the United States, most people spend about 90 percent of their time indoors. The purpose of
specifying the indoor design conditions in the design documents is to provide the occupants with a
satisfactory indoor environment at optimum cost.
After the energy crisis in 1973, a lower outdoor ventilation rate, a tighter building shell, and the
use of variable-air-volume (VAV) systems at part-load operation may reduce the amount of outdoor
air intake significantly. Indoor air quality therefore has become one of the critical HVAC&R problems
especially in commercial buildings since the 1980s.
Based on the results of the field investigations of three office buildings by Bayer and Black in 1988,
the indoor air contaminants that relate to indoor air quality and the symptoms of the sick building
syndrome are mainly the following: