The New York Police Department on Monday began pumping "tracer gases" through the New York City subway system as part of efforts to learn what the ramifications might be if terrorists attempt to carry out a chemical gas attack, the New York Daily News reported.
The gases used in the study were innocuous, unreactive, invisible and without odor, sources told the paper. They were to be pumped into underground chambers throughout the city at three different points. Approximately 200 air monitors were to be located throughout New York's vast subway system to collect samples from the test.
Findings from the research will be used to create emergency-reaction plans for handling a chemical terrorist attack. Financing for the test comes from the federal government.