Sandia LabNews

Labs experts helping evaluate security at US chem plants

With anthrax making its deadly appearance on the East Coast, one question keeps emerging in the minds of many Americans. How can we protect our buildings from chemical and biological attacks?

A Sandia team led by Richard Griffith (9117) has developed modeling and simulation tools for assessing the threat and vulnerability of buildings to such assaults. This includes looking at how chemical and biological agents move and deposit inside a building, developing and assessing mitigation strategies, guiding the use of detection methods, and examining the effectiveness of cleanup and decontamination efforts.

Richard began working on the project following the 1995 sarin gas release in Tokyo’s subway system, where it became apparent that chemical and biological attacks by terrorists could be a trend of the future. Over the last few years a large team of Sandians, scattered across several divisions and both sites, has worked to develop and apply these modeling and analysis capabilities. Interest from government agencies and others in the work has skyrocketed since Sept. 11.

Using sophisticated Sandia-developed computer modeling and visualization capabilities, the team can simulate how various chemical and biological agents — such as anthrax, smallpox, sarin, and mustard gas — flow through a building and deposit on various surfaces.

"We start by mapping out the building and creating a computational model from the electronic AUTOCAD blueprints, including all the rooms and areas served by each air handler and all the air ducts," Richard says. "Then we simulate the release of a chemical or biological agent directly into different parts of the building, or from the outside for exterior releases."

The computer model, known as KCNBC, predicts where the agent will move as a function of time following its release, producing a movie that gives researchers a view of agent transport and concentration. Simulations include a variety of agent release scenarios using real properties for a number of chemical and biological materials.

Modeling applied to several facilities

This modeling capability has been applied to several facilities, including an eight-story federal courthouse, a military command and control center, and a large airport terminal building.

And since Sept. 11 Richard has received numerous inquiries from government agencies and others about how to assess the chem/bio threat and the vulnerabilities of their buildings.

The information produced by the computer simulations becomes extremely valuable in determining cost-effective mitigation strategies, figuring out where to put agent detection sensors, sensor performance requirements, and deciding on cleanup and decontamination tactics.

In the area of mitigation, for example, the simulations might provide insight as to whether some or all of the air handlers should be turned off in a contaminated building, if it would be effective to purge out the contaminated air and pump in fresh air, if it might be possible to contain or isolate the agent using the HVAC (heating, ventilation, air conditioning) system, or if filters or neutralizers should be used. The benefits of any given mitigation strategy can be assessed to help pick the most useful or cost-effective approaches to protecting the building.

The modeling data could also guide the optimal placement and use of the sensors used to detect chemical and biological agents.

"These new sensors are expensive, and may have significant installation and maintenance costs," Richard says. "If you can have only five or six of them to help protect a large building, you have to figure out the most effective places to put them."

The question then arises of how sensitive the sensors must be and how fast must they respond. For example, asks Richard, would a sensor with a five-minute response time help and where would fast or slow sensors be appropriate? What sensor sensitivity is needed to effectively protect the building by initiating active responses? The modeling and simulation tools help to answer those questions.

Cleanup and decontamination efforts could also benefit from computer modeling. The models can predict agent deposition on floors, walls, ceilings, ducts, and other surfaces in every room of the building, telling researchers where the agent could go and what areas of a building could be the most contaminated. The information could allow cleanup efforts to be focused on the most contaminated areas, giving insight about where cleanup efforts should begin and where they are less needed.

"Smart building"

Finally, Richard says, the modeling and analysis tools are critical technologies in creating a "smart building," one that integrates sensor information and observations from human security to "know" what is happening in and around the building, and then uses predictive modeling and decision-making algorithms to chose the most effective responses to protect building occupants. When sensors detect the presence of an agent, a "smart building" would chose the best HVAC system response to create clear evacuation paths or areas of the building where occupants could take shelter, provide real-time instructions to occupants and first responders, and minimize the amount of the building that was contaminated.

"There are a lot of things we can do to make sure that buildings in America are safe from chemical and biological agent attack," Richard says. "These modeling and analysis tools can play a key role."