Environmental Engineering Reference
In-Depth Information
remain after millennia, they have long ceased to shelter humans and their
activities. Wooden structures that housed humans for much of our history
have been turned to mould. Indeed, the contagion of decay, fed by neglect
and the forces of wind and water, constantly imperil even our newest struc-
tures. They may even affect our health and make our dwellings unclean. The
topic of Leviticus in the Old Testament of the
Bible
describes a “leprous”
house and what is to be done about it.
“If the priest, on examining it, finds that the infection
on the walls of the house consists of greenish or red-
dish depressions which seem to go deeper than the
surface of the wall, he shall close the door of the house
for seven days. On the seventh day, the priest shall
return to examine the house again. If he finds that the
infection has spread on the walls, he shall order the
infected stones to be pulled out and cast in an unclean
place outside the city. The whole inside of the house
shall be scraped, and the mortar that has been scraped
off shall be dumped in an unclean place outside the
city. Then new stones shall be brought and put in the
place of old stones, and the new mortar shall be made
and plastered on the house.”
Though we design buildings and other structures to provide shelter from
an often hostile outdoor environment, the shelter they provide is less than
perfect. They are subject not only to the forces of nature, but also to the
randomness inherent in the second law of thermodynamics or its derivative,
the law of unintended consequences.
As we attempt to provide both shelter and those many amenities and
conveniences that make life more comfortable, we, in many cases inadvert-
ently and in other cases deliberately, introduce a variety of contaminants
that have the potential to diminish the quality of our lives or pose moderate
to significant health risks to occupants.
Indoor environments are often contaminated by a variety of toxic or
hazardous substances, as well as pollutants of biological origin. When early
humans discovered the utility of fire and brought it into rock shelters, caves,
and huts, they subjected their sheltered environments to the enormous bur-
den of wood smoke (not much different from modern cooking fires in devel-
oping countries) and attendant irritant and more serious health effects. Bio-
logical contaminants such as bacteria, mold, and the excretory products of
commensal organisms (e.g., dust mites, cockroaches, mice, etc.) have caused
human disease and suffering for most of human history. However, viewed
within the context of infectious and contagious diseases such as tuberculosis
and bubonic plague, illness caused by asthma and chronic allergic rhinitis
can be seen as relatively minor.
