Page 447 - Air pollution and greenhouse gases from basic concepts to engineering applications for air emission control

428 14 Indoor Air Quality

increase in the awareness of indoor air pollution with the advances of research and
education in related field.
Increasing attention to indoor air quality was largely attributed to the awareness
of poor health associated with the poor indoor environment. According to the
studies sponsored by the US EPA, concentrations of indoor air pollutants may be
2–5 times, and sometimes, over 100 times higher than their outdoor counterparts,
and indoor air pollution is one of the top five environmental risks to public health,
comfort, and performance [1]. The situation is believed to be worsening with
reduced ventilation rate for energy conservation and increased use of chemically
formulated household products, and emissions from electronic office products.
Indoor air pollution has a profound impact on the quality of life and the econ-
omy. The National Institute for Occupational Safety and Health (NIOSH) ranked
occupational lung dysfunctions (including lung cancer, pneumonoconioses, and
occupational asthma) as the top occupational diseases and injuries. Lung dys-
function is undoubtedly related to the indoor air quality that people are exposed to.
In some extreme case, indoor air pollutant could cause death.
Illnesses related to indoor air pollution can be classified into two categories:

• Sick building syndrome (SBS)
• Building related illness (BRI)
SBS is defined as the discomfort or sickness associated with poor indoor air
quality without clear identification of the source substances. These symptoms could
be, but are not limited to, irritation to eyes, noses, or throat, fatigue, and nausea.
BRI is defined as a recognized disease caused by known agents that can be clini-
cally identified. Examples of SRI symptoms include asthma, legionella, hyper-
sensitivity, and humidifier fever. Obviously, the difference between the SBS and
BRI is whether the causes of the sickness can be diagnosed clinically. Most of the
time, the general public do not differentiate them, and they both are often referred to
as sick building syndrome. Approximately one million buildings in the United
States are sick buildings with 70 million occupants [2].
It is challenging to list all the sources of indoor air pollutants. Nonetheless, they
can be grouped into outdoor and indoor sources. Outdoor air contaminants can enter
indoor environments through HVAC systems, building envelopes, or even windows
and doors. Indoor sources include combustion sources, such as smoking and
cooking, operation of equipment, such as printers and computers, and biological
sources, such as plants, animals, and human beings.
An incomplete list of sources of indoor air pollutants (excluding those with
outdoor origins) is shown in Table 14.1. The list cannot be complete because of the
nearly infinite contaminants in the air and multiple sources of each pollutants.
Therefore, this table shall be used for guidance only.
Asbestos is a set of six naturally occurring silicate minerals used commercially
for their desirable physical properties. They all have in common their eponymous
asbestiform habit: long (roughly 1:20 aspect ratio), thin fibrous crystals.
The prolonged inhalation of asbestos fibers can cause serious illnesses including
malignant lung cancer, mesothelioma, and asbestosis. Asbestosis is most closely