NEW YORK (CBSNewYork)– Starting Monday, a massive study will begin to examine the airflow through tunnels in the New York subway in case they’re ever targeted in a terror attack.

If you’re traveling through the subway system this week, you may spot a small device that could play a big role in the war on terror, CBS2’s Hazel Sanchez reported.

“This is important information to help local authorities enhance their emergency preparedness for an event that might occur in the subway if there’s a release of biological material or a chemical material,” Dr. Donald Bansleb with Homeland Security said.

In preparing for a potential biological chemical attack, the Department of Homeland Security and New York Metropolitan Transportation Authority will be placing about 200 chemical tracers at dozens of subway stations across the city.

As part of a five-day airflow test there will be scheduled releases of a safe, harmless gas from Grand Central Terminal, Penn Station, and the Times Square Station.

“This will tell us in real time data aerosol concentrations and the particle concentrations in the stations after we do the release,” laboratory engineer David Brown said.

“That will help authorities to predict boundaries of contamination if there is a release of a substance,” Bansleb said.

Subway riders said they’re glad to see the city being proactive.

“I think that all kinds of testing to just cover all bases to see that we’re safe. That seems reasonable,” Upper West Side resident Elizabeth Graham said.

“It gives us an opportunity to open our eyes to see the times we  are living in. It’s something good,” subway rider Jose Gomez said.