Homeland Security tests subway systems

Scientists working for the Department of Homeland Security have recently been testing the air flow of the Boston and Washington, D.C., subway systems in order to devise a better response to a terrorist attack using biological weapons.

Teams of researchers placed electronic monitoring equipment in the systems to trace the behavior of airborne contaminants. The studies were done in two phases. The first portion was conducted in December 2009, and the second in August 2010, according to CSOOnline.com.

"The movement of airborne contaminants can be affected by differences in temperature and humidity, so a comprehensive study requires gathering data in both winter and summer months," Program Manager Teresa Lustig said, according to CSOOnline.com. "In addition to comparing the effects of seasonal conditions, a second phase of the study also allows us to test the effectiveness of some of the proposed countermeasure and response strategies derived from analysis of the December tests."

During the testing, two types of innocuous tracer gases -  sulfur hexafluoride and perfluoro-carbon - were released in the subway systems. Both of the gases are stable, colorless, odorless and non-combustible. They have been used as tracers since the 1960s because they move through the air like a chemical agent and can give scientists an idea of just how quickly an airborne contaminant can spread in a closed space.

"Once an aerosol is released into the air, it takes awhile for it to settle," researcher David Silcott, general manager of IBX Biodefense, said, according to CSOOnline.com "Once a train comes along, it pushes it down further into the system."

Particle and gas concentrations were tested at 20 different stations and in subway cars throughout the Boston subway system. Boston’s system was chosen, in part, because it is one of the nation’s oldest and was built in separate stages. The system in Washington was chosen, in part, because it is one of the nation’s newest.

“By looking at the data we collect from the two vastly different systems, we can apply what we learn to other subways systems across the nation and to our international partners—all in the effort to keep travelers safe." Lustig said, CSOOnline.com reports.

The results of the research will help authorities develop a plan to detect an attack quickly so that the proper areas of the subway can be shut down to limit contamination. They will also help determine routes of evacuation and ventilation strategies.