Decades of Secret Testing In The NY Subways (VIDEO)

Editor's note: Recall scientists from the Fort Detrick biological weapons program releasing nontoxic bacteria in the New York subway in the 50s and 60s.

The New York City Police Department announced Wednesday that it will deploy, then track, what it calls "harmless" gases into the city's subway system over three non-consecutive days this summer. 

The plan, to be enacted in July, will investigate New York's readiness to handle a chemical terrorist attack by dispersing the colorless gas and tracing it as it flows through the city, according to Scientific American. The test is expected to cost $3.4 million and is scheduled to be carried out in all five boroughs and dozens of stations on 21 of the city's 34 subway lines.

"The NYPD works for the best but plans for the worst when it comes to potentially catastrophic attacks such as ones employing radiological contaminants or weaponized anthrax," police commissioner Ray Kelly said in a statement.