Environmental Engineering Reference
In-Depth Information
4.
Evaluating effectiveness of mitigation measures
Environmental sampling is routinely used to test the effectiveness of radon
mitigation measures. This requires that sampling be conducted prior to and
after mitigation activities have been completed. Environmental sampling is
also conducted to determine the effectiveness of post-abatement cleaning
measures for asbestos and lead in buildings, and is increasingly being used
to determine the effectiveness of clean-up activities after the abatement of
toxigenic mold infestations such as
Stachybotrys chartarum
and
Aspergillus
versicolor
. In asbestos abatements, aggressive sampling is conducted to meet
clearance airborne asbestos fiber concentrations; it is also a desirable practice
in toxigenic mold abatements. Surface sampling is conducted in lead abate-
ments to determine whether clearance guidelines have been achieved.
Environmental sampling has particular value in determining the effec-
tiveness of measures implemented to improve ventilation. Pre- and post-
measurements of CO
levels are commonly conducted to evaluate the per-
formance of ventilation systems after operation and maintenance changes
have been made.
Environmental sampling in conjunction with occupant health and com-
fort surveys can be used to evaluate the effectiveness of mitigation efforts
in reducing symptom prevalence and increasing occupant satisfaction with
air quality. Such coordinated pre- and post-environmental sampling and
occupant health and comfort surveys are rarely conducted. Those conducted
in research studies have, for the most part, not demonstrated significant
reductions in symptom prevalence rates and increases in occupant satisfac-
tion with air quality.
2
C. Sampling airborne contaminants
Airborne gas and particulate-phase substances have historically been the
major focus of environmental sampling in indoor environments subject to
indoor air quality/indoor environment (IAQ/IE) concerns. The conduct of
air sampling requires selection of appropriate sampling and analytical pro-
cedures including: (1) instrument selection and calibration; (2) sampling
location, time, and duration; and (3) number of samples. It also involves
sampling and analysis administration and quality assurance.
There are a variety of approaches, sampling instruments, and analytical
methods that can be used to conduct measurements of airborne contaminants.
Selection of sampling and analytical techniques that provide acceptable per-
formance is, of course, very important. Acceptable performance is ensured
by implementing appropriate quality assurance practices. These performance
considerations include accuracy, precision, sensitivity, and specificity.
1.
Performance considerations
Accuracy is the closeness of a value to its true or known
value. It can be described by an error value expressed as a percentage. A
a.
Accuracy.
