The MTA began an air sampling study on Monday, which involves teams releasing non-toxic gases into the air at 120 above- and below-ground locations. According to the federal Urban Threat Dispersion program, "The purpose of the tests is to collect quantitative data and information on the transport and deposition of particles that simulate the release of a biological agent in a major metropolitan area and to evaluate the sensor architectures for rapid detection and mitigation of a chemical-biological event in the subway."
The Department of Homeland Security is leading the work, along with the MTA, the NYC Emergency Management, and Massachusetts Institute of Technology. The study, which takes place over five days, will conclude on October 29th.
The study is also interested in locations with high commuter density at peak or near-peak hours, and with that in mind, some of the citywide locations will include platforms at Times Square and Union Square subway stations, and inside the Oculus. Outdoor locations will include Times Square, the World Trade Center Complex, and Union Square Park. The DHS's Science and Technology Directorate explained in a report that they are looking at areas with "multiple subway lines converge, high passenger and pedestrian traffic, significant cultural and economic importance, etc." for the test.
Subway riders will notice sampling devices, aerosol release devices, and gas sensors. Here's what it looked like in 2016:
"During the course of testing, customers using the system may see staff performing test and sampling operations. The study will track movement of non-toxic material and the results from these tests will be used to learn more about the relationship between airflow in street level and underground environments," the MTA said in a press release.
The agency emphasizes that there are no health risks to the public. Some of the particles proposed for the test include chemicals like maltodextrin (what's used in Splenda) and amorphous silicia, which was used in the 2016 air sampling study, the DHS said, "with no reported adverse side effects."
