Building Retrofits for Increased Protection Against Airborne Chemical and Biological Releases.
Building Retrofits for Increased Protection Against
Airborne Chemical and Biological Releases.
(9097 K)
Persily, A. K.; Chapman, R. E.; Emmerich, S. J.; Dols,
W. S.; Davis, H.; Lavappa, P.; Rushing, A. S.
NISTIR 7379; 179 p. March 2007.
Sponsor:
Environmental Protection Agency, Research Triangle Park,
NC
Keywords:
air cleaning; building protection; chembio; filtration;
indoor air quality; life cycle costs; terrorism;
scenarios; simulation; office building; high rise
buildings; evaluation; costs
Abstract:
Due to concerns about potential airborne chemical and
biological (chembio) releases in or near buildings,
building owners and managers and other decision makers
are considering retrofitting buildings to provide some
degree of protection against such events. A wide range
of technologies and approaches are being proposed with
varying levels of efficacy and cost, as well as varying
degrees of applicability to particular buildings and
ventilation systems. This document presents the results
of an effort to evaluate chembio retrofit options for
buildings. A number of retrofit options are identified,
and their potential to protect building occupants from a
number of generic contaminant releases is evaluated
using building airflow and contaminant transport
modeling. In addition, a case study is presented in
which specific retrofit options were considered for two
actual buildings and pre-installation designs and cost
estimates were developed. Based on the analyses
performed, the results of the case study and other
available information, guidance on the application and
effectiveness of various retrofits are presented. An
economic analysis software tool employing life cycle
cost analysis techniques was developed as part of this
project, and its use is described in an appendix to this
report. The retrofit options considered fall into two
categories, the first being stand-alone technologies
or devices such as enhanced particulate filtration that
are installed and implemented as purchased. The second
category includes retrofit approaches that employ
operational strategies or building modifications to
increase building protection, such as outdoor air
purging or building envelope air tightening. The
guidance section describes each retrofit technology and
approach in some detail, presenting relevant performance
data and the level of protection that might be expected
from the retrofit. Potential disadvantages and knowledge
gaps are also discussed for each technology. The
retrofit technologies considered include enhanced
particle filtration, sorbent based gaseous air cleaning,
ultraviolet germicidal irradiation, photocatalytic
oxidative air cleaning, and work area air capture and
filtration equipment such as mail handling tables. The
approaches include ventilation system recommissioning,
building envelope airtightening, building
pressurization, relocation of outdoor air intakes,
shelter-in-place (SIP), isolation of vulnerable spaces
such as lobbies, system shutdown and purge cycles, and
automated heating, ventilating and air-conditioning
(HVAC) operational changes in response to contaminant
sensing. The filtration and air cleaning options are
noted to have an advantage of always being operational,
which is an advantage as long as the systems are
properly designed, installed and maintained. However,
the lack of standard test methods for sorbent-based
gaseous air cleaning and other air cleaning approaches
is identified as a critical issue in the application of
these technologies. Building envelope air sealing and
pressurization can be quite effective in protecting
against outdoor releases as long as effective filtration
against the contaminant of concern is also in place. The
protection provided by operational changes such as
system shutdown and purging are shown to be very
dependent on the timing of their implementation, with
the possibility of increasing occupant exposure if the
timing is inappropriate. Isolating vulnerable zones and
other system related modifications are highly dependent
on the building layout and system design, and their
implementation must be well conceived to be effective
under the range of conditions that exist in buildings.
Finally, many retrofits are noted as also providing
additional benefits of increased energy efficiency and
improved indoor air quality, which should be included in
the life-cycle cost comparison of different options to
the degree possible.
Building and Fire Research Laboratory
National Institute of Standards and Technology
Gaithersburg, MD 20899