January 2000

List questions and answers here. Engineers Develop System To Assess Anthrax Threats

By Rachel Davis
Associate Editor

How do companies guard their employees against an enemy they can't see? Over the last several months, anthrax contamination reared its head at dozens of sites in the U.S., resulting in the deaths of five people. In this cautious environment, companies are seeking the right level of response to protect their staff from possible biological or chemical contamination in a way that's unobtrusive, yet effective.

Two NSPE members from South Dakota are helping employers with this dilemma by working with an indoor air quality testing company to develop a threat-analysis system to reduce the impact of biological and chemical attacks.

NSPE member and Professional Engineer George Dunham received a telephone call from Gray Robertson, president of Virginia-based Healthy Buildings International Inc., shortly after the first case of anthrax was reported in Florida on September 18. Robertson wanted Dunham's help in coming up with a process that HBI could use to evaluate the vulnerability of buildings to chemical and biological attacks and propose appropriate solutions.

Dunham and Robertson, who have been friends for 10 years, worked together on significant air quality and ventilation projects for large companies in the past. Dunham, who specializes in HVAC design, founded the 41-year-old consulting engineering company Dunham Associates Inc. with his wife and fellow NSPE member, Professional Engineer Nancy Dunham. Although he retired and sold his interest in the company in 1999, Dunham was willing to take on the threat-analysis project.

NSPE members Steve Malone, P.E. (left), and George Dunham, P.E., of South Dakota

Although Dunham and Robertson outlined their threat-analysis plan in one day, they honed the idea over the next few weeks. The beginning phase of the plan, vulnerability assessment, is composed of several steps. The first step, data gathering, involves collecting as much physical data about the structure of the building as possible, focusing on features such as the HVAC system and air filters, vertical shafts, atria, and stairwells.

For the second step, Dunham recruited NSPE member and Professional Engineer Steve Malone, founder of South Dakota's Malone Engineering, to develop three-dimensional computer models of airflow, using computational fluid dynamics software to analyze various attack scenarios. Dunham had hired Malone out of college and mentored him for about 15 years. About the time Dunham retired, Malone started his own company.

The computer models can be used to track the source of a contaminant and study how it spreads within a building. For example, given the right parameters, the software tracks how wind and thermal currents would carry a contaminant and shows whether it would enter the inside air intakes. Running a typical 3D model of airflow can take more than 36 hours, Dunham says.

The third step is a physical test, which involves releasing an inert "tracer" gas in the building and using infrared photography and thermal imaging to identify cracks or other deficiencies in the building structure.

After the vulnerability assessment is complete, the next step is to identify the problems and propose solutions. HBI mechanical engineers could assess how contaminants would get around the building, and then devise methods to minimize and control contamination. This may involve changing the direction of airflow or using sophisticated, clean room-type filters to capture biological or chemical hazards, Dunham says.

The threat-analysis system has drawn the attention of several federal agencies, and there appears to be significant consumer demand in HBI's future, he says. The company is currently implementing its threat-analysis plan for its first client, the Federal Reserve Bank system.

Depending on the building size or complexity, the vulnerability assessment phase of the threat-analysis system would cost a client $20,000 to $40,000, Dunham says. "Once you've identified the problems, then solutions cost more," he adds.

One of the problems with detecting anthrax is that there are no means of immediately identifying the bacteria without taking samples to a lab. This process takes at least 24 hours, Dunham says. "Proper air filters can go a long way toward preventing the spread of contamination within a building. However, once you've trapped them in the filters, you have to know they are there."

At 67 years old, Dunham has temporarily come out of retirement to be integrally involved with setting up the threat-analysis plan for HBI's first clients. As for how long his involvement with the project will last, he chuckles, "It's like dipping your toe into a swiftly flowing river and trying not to get swept away."