Article

HVAC design and operations in response to homeland security issues-a decision-making process

Authors:
Article

HVAC design and operations in response to homeland security issues-a decision-making process

If you want to read the PDF, try requesting it from the authors.

Abstract

Since the terrorist attacks on 911 the safety and security of occupants in at-risk buildings has been elevated in importance for the design and operations of buildings. With a high level of occupant safety as a goal, architects, and structural and mechanical engineers must work collaboratively. This is particularly true for decisions related to the design and operation of heating, ventilating and air-conditioning (HVAC) systems. Generally terrorist attacks on buildings will be the result of either detonation of an explosive devise or release of a chemical or biological agent. It is this latter approach that is of most concern for the design and operations of HVAC systems as they may reduce or increase risk depending on their operation. This paper presents the beginning of a decision-support framework for the design of buildings and HVAC systems to reduce the risk to occupants in the event of a release of a chemical or biological agent. The paper attempts to identify issues that should be considered by architects and HVAC engineers during the design process. The paper proposes that design and operations decisions are based on risk assessment, owner/design goals, constraints, performance satisfaction, and cost assessment. An overview of these decision-making factors is discussed as they relate to HVAC systems.

No full-text available

Request Full-text Paper PDF

To read the full-text of this research,
you can request a copy directly from the authors.

... Typically this guidance is high level in nature, and often deals only tangentially with the CB threat. For example, Jones and Singh (2008) outline a design process that takes into account risk assessment (specifically tailored to the CB threat), but which is still qualitative in nature. ...
Article
Quantifying the impact of chemical or biological releases on a building and its occupants is a necessary part of risk assessment. The most informative metrics for this purpose are absolute, "threat-based" measures of lost or preserved assets that are specific to the agent of interest. Practical application of threat-based metrics may be difficult because data such as the maximum plausible release quantity and dose response characteristics for an agent may be unavailable. In addition, it is left to the judgment of the analyst to select appropriate agents on which to base risk management decisions. Relative metrics are an alternative to absolute metrics that compare quantities such as exposure without respect to the specific agent. Such metrics may be described as "vulnerability-based" because their values reflect the influence of the building and its systems on exposure, independent of the agent. Vulnerability-based metrics are generally easier to determine but harder to interpret than threat-based metrics. The ordered, area-weighted distribution of concentration raised to a power corresponding to the toxic load exponent of an agent was selected for investigation as the basis of a vulnerability-based metric. Metric values were computed from concentration time histories generated by multizone model simulations of indoor agent releases. It was found that metrics derived from this distribution can distinguish between the severity and extent of different releases. Although easier to apply to the results of multizone modeling, the proposed metric can, in principle, also be applied to experimental data.
Article
The current design guidelines and field practices for room pressurization were investigated. As such, some practical in-field design considerations for two types of facilities were examined. These, in particular, were a tuberculosis BSL-3 research lab and a health-care hematopoietic stem cell transplant unit. In addition to field tests, the author provides a methodology for practitioners for verifying airflow direction, into or out of the room.
Article
Ventilation and air distribution are critical with respect to the issues of airborne chemical, biological and radiological (CBR) agents entering buildings, their movement within the building and their subsequent removal. To effectively address these issues, it is important to understand what the system is intended to do, and what it is actually doing. A number of strategies exist using ventilation to limit the impact of CBR events in buildings. Fist is to isolate vulnerable spaces where it might be easier for an agent to be released into a building. Second is to increase the level of filtration. Third is to use ventilation, tight interior partitions and sometimes local air cleaning systems to create a safe area or refuge where people can congregate during a CBR release. Finally, changes in HVAC system operation can be implemented based on CBR agent detection to achieve isolation of contaminated spaces and provision of safe egrees paths or safe refuges for building occupants. While none of these four options will provide complete protection against all challenges, they can at least increase the degree of protection.