NEW YORK (WABC) --Just how vulnerable is the New York City subway system with its millions of riders? That is one of the questions this week's Homeland Security airflow study is designed to answer.
By releasing non-toxic gases and particles on crowded subway platforms, scientists will be able to measure the impact of a chemical or biological terrorist attack.
"How far it moves, what the dilution is, what the concentrations are, how it moves from line to line for instance - things like that," says Research Scientist David Brown.
Every day this week, particles will be released, and busy stations like Grand Central Terminal and Times Square and Penn Station, special machines and filters on platforms and subway cars will collect the data.
Most riders will be unaware of the important work underway. Those who watch the testing again, told Eyewitness News that they liked the idea.
"It's a shame that we have to live the way we do today, that terrorism is a way of life. However, I'm glad to see the city taking action to protect the people that are riding the subway," says Greg Moshensky.
"I think that it's needed this way...in terms of emergency, we can have a better evacuation plan," says Keith Davis.
The riders share the thinking of the FDNY, not surprisingly more than a little interested in what the data collected ultimately shows.
"It helps us better understand where the material is, how far it travels, what concentration, and then we can determine what we need to do to better prepare," says FDNY Battalion Chief Bob Ingram.