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 airtightening. 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 airconditioning (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 ...

ii iii ABSTRACT Due to concerns about potential airborne chemical and biological releases in or near buildings, building owners and managers and other decision makers are faced with a number of options for increasing their building's level of protection against such events. Among the various technologies and approaches being proposed and implemented is shelter-in-place (SIP). SIP strategies involve having the building occupants stay in the building, generally in a space designated for such sheltering, until the event is over and the outdoor contaminant levels have decreased. While much guidance is available on the implementation of SIP in buildings, important technical issues remain about the degree of protection provided by a particular space and the factors in determining the level of protection. In particular, many recommendations suggest tightening the walls of SIP spaces, but there has been insufficient analysis of the relationship between shelter tightness and the protection provided by the SIP space. In order to address some of these questions, the National Institute of Standards and Technology (NIST) has undertaken a project for the U.S. Environmental Protection Agency to develop and demonstrate evaluation methods to relate shelter airtightness to the performance of shelter-inplace approaches for airborne chemical, biological and radiological (CBR) protection of building occupants. The focus of this effort is on short term sheltering, on the order of hours, rather than longer term sheltering which generally employ filtration and air cleaning equipment to supply clean air to the occupants of the space. This project has consisted of the following tasks: a literature review of SIP strategies and performance issues; development of a study plan for testing SIP airtightness evaluation methods; implementation of the study plan through a combination of experiments and simulations; and, finally, development of recommendations on SIP evaluation and possible performance criteria for candidate SIP spaces.

Concerns about building security have resulted in increasing interest in gas phase air cleaning (GPAC) and the need for standard methods to determine the effectiveness of these systems. Similarly, the ability to predict their installed performance, based on such standard test data, is becoming increasingly important. The development and application of these standards and prediction tools will provide better protection of building occupants against chemical agents and improve the ability of designers and building owners to identify and specify air-cleaning equipment with a realistic expectation as to installed performance. The National Institute of Standards and Technology (NIST) has conducted an effort to facilitate the development of these standards and predictive tools under a project funded by the Department of Homeland Security. This report describes the following tasks that were carried out as part of this project: an evaluation of gas phase air cleaning technology; an assessment of existing and proposed standards, as well as relevant guidance documents; design of a laboratory-scale microreactor to evaluate media consistent with current and proposed industry approaches; micro-scale modeling to understand the interactions between the media and gaseous contaminants and, building-scale modeling to understand the impacts of air cleaning systems in controlling occupant exposure.

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