Page 554 - Mechanical Engineers' Handbook (Volume 4)

4 Indoor Air Quality (IAQ) 543

concentrations and the majority of occupants (more than 80%) express satisfaction. Indoor
air quality plays a significant role in occupants’ well-being, satisfaction, and health, due to
the prolonged time periods spent indoors in a modern society.

4.1 Health Issues and Requirements

Buildings with poor air quality have produced many occupant health complaints/illnesses/
conditions that have been recorded and labeled ‘‘sick building syndrome’’ (SBS). SBS is
discomfort/illness caused by indoor air. Symptoms are often comparable to a cold or influ-
enza, such as headaches, drowsiness, eye irritation, and nose and throat infection. The main
difference between SBS and a cold is that the SBS symptoms last much longer than cold
symptoms and disappear after the occupant leaves the building. Approximately 30% of new
or remodeled buildings produce health complaints as reported by Environmental Protection
Agency (EPA). Indoor air contaminant levels can be several magnitudes greater than the
outdoor air contaminant levels due to the contaminant releases from building materials,
occupants, or different building processes. Table 2 shows a few contaminant sources, per-
mitted levels, and possible health effects according to EPA standards. Regardless of permitted
levels, the actual response to a contaminant is based on the individual.
As listed in Table 2, indoor contaminants could be particles or gases and vapors. Par-
ticles could be allergens, molds, bacteria, dust, fumes, smoke, or mist and fog. Contaminant
gases could be inorganic or organic. Harmful inorganic gases, such as radon (a radioactive
gas), have the potential to cause lung cancer due to the particle deposition in lungs. Harmful
organic vapors may cause major respiratory irritation and may be perceived as unpleasant
odors. In the worst-case scenario, harmful vapors could be completely odorless. Many paints
waxes, varnishes, and cleaning products are rich in organic solvents that evaporate even
without use. Table 3 shows human irritation responses to total volatile organic compound
(TVOC) mixtures based on a human subject study in a controlled laboratory environment
(Molhave et al., 1991).

4.2 Problem Mitigation
Numerous indoor air-quality investigations over the last decade by the National Institute for
Occupational Safety & Health (NIOSH) have found that primary sources of indoor air-quality
problems are

Table 2 Contaminant Sources, Permitted Levels, and Health Effects (EPA)
Contaminants Sources Permitted Levels Health Effects
Human, combustion 1000 ppm Stuffing
CO 2
CO Combustion, ETS 15 ppm Body chemistry
Combustion Irritation, asthma
SO x
Combustion 100 g/m 3 Not very clear
NO x
Ra Soil 4 picocuries/L Lung cancer
VOCs (formaldehyde) Combustion, pesticides, 0.1 ppm Eyes and mucous
building materials, etc. membrane
irritation
Particulate Outdoor air, activities, Lung diseases
(0.01 micro-insects) ETS, furnishings, pets, Cancer (ETS)
etc