Environmental Engineering Reference
In-Depth Information
nishings, and a variety of occupant activities. In the IAQ Option or Proce-
dure, building designers could use any amount of outdoor air as long as
guideline values of specific contaminants such as formaldehyde (HCHO),
ozone (O
), etc., were not exceeded. The IAQ Procedure was intended to (1)
encourage innovative energy-conserving solutions for providing building
ventilation and (2) give recognition to the fact that ventilation standards
based on bioeffluents alone were not adequate to deal with the many con-
taminant problems that exist in indoor spaces.
Before the IAQ Procedure could be used by design engineers, it would
be necessary to develop performance standards from knowledge of the
health effects of all or targeted pollutants in a building. Acceptable levels
would be set after the relative risks of exposures to specific contaminants
had been determined. A prescriptive path would be developed to give build-
ing designers specific procedures to satisfy performance standards. This
would include upper bounds on source strength and lower bounds on ven-
tilation rates required. These bounds would be determined from air quality
models designed to simulate contaminant emissions and transport, ventila-
tion parameters, and occupant exposures.
The IAQ Procedure makes considerable sense from a scientific perspec-
tive because it focuses on the problem of controlling a variety of contami-
nants which may adversely affect air quality and pose health risks. Not
surprisingly, the IAQ Procedure has rarely been used to design building
ventilation systems. Unlike the Ventilation Rate Procedure, which is known
for its simplicity and long history, the IAQ Procedure is characterized by
knowledge requirements that are beyond those of the average design engi-
neer and numerous uncertainties related to the health effects of targeted
contaminants, acceptable levels of exposure, sources and their emissions,
and how installed ventilation systems will actually perform to achieve IAQ
Procedure objectives.
The IAQ Procedure requires development of guideline values for accept-
able levels of specific contaminants. Manufacturers of products that emit
contaminants may not accept the fact that their products are unsafe (i.e., they
emit contaminants that exceed acceptable guideline values). A classic case
of this has been HCHO. In 1981, ASHRAE published a guideline value for
HCHO. After being threatened with a lawsuit by wood-products manufac-
turers and others, ASHRAE deleted HCHO from its guideline values in 1989
(and placed other guideline values in the appendix).
Despite new efforts to revive it (see Chapter 13), the IAQ Procedure has
a limited future relative to its general use as a ventilation specification tool
in designing buildings. Any appeal that it has is lost in the complexities of
its use and the politics of prescribing guidelines for acceptable contaminant
levels. Variations of this concept have received limited application. In Wash-
ington, new state office buildings must use materials that meet emission
limits under specified ventilation conditions. A number of other large build-
ings in the U.S. have also been constructed using IAQ Procedure concepts.
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