A multi-year initiative at MIT Lincoln Laboratory aimed at analyzing the dispersion of biological and chemical vapors and aerosols throughout the New York City subway system is nearing completion. This program, part of the U.S. Department of Homeland Security (DHS) Science and Technology Directorate’s Urban Area Security Initiative, builds upon existing efforts at Lincoln Laboratory to detect chemical and biological hazards, corroborate air dispersion models, and enhance emergency strategies in urban settings in the event of an airborne assault. The findings from this initiative will guide the New York Metropolitan Transportation Authority (MTA) on the most effective and economical means to implement a system for airborne threat detection and mitigation within the subway system. More broadly, the research will assist the national security sector in comprehending practical chemical and biological defense solutions for mass transit, vital facilities, and significant events.
Trina Vian from the laboratory’s Counter–Weapons of Mass Destruction (WMD) Systems Group spearheaded this project, which she asserts encompassed not only air flow and sensors but also MTA protocols and the experiences of NYC commuters. “There are genuine risks linked to panic during an alert. Individuals can sustain injuries during mass evacuations, or they may lose faith in a system and the authorities overseeing that system if false alarms occur,” she explains. “A distinctive element of our project was to explore effective low-regret response options, which entail minimal operational repercussions in response to a false alarm.”
At present, depending on the alarm’s intensity, the MTA’s reaction may involve halting service and evacuating both passengers and employees.
A challenging testing environment
For this program, initiated in 2019, Vian and her team gathered data on how chemical and biological sensors functioned in the subway, what factors influenced sensor reliability, and how various mitigation strategies performed in curbing the spread of airborne threats and eliminating hazards from contaminated sites. They released batches of a harmless, specially designed aerosol simulant within Grand Central Station, which they monitored using DNA barcodes. Each batch carried a unique barcode, allowing the team to distinguish between them and quantitatively evaluate different combinations of mitigation approaches.
To manage and control air flow, the team examined static air curtains as well as air filtration systems. They also tested a spray knockdown system developed by Sandia National Laboratories, designed to diminish and isolate particulate hazards in large spaces. This system projects a fine mist of water into the tunnels that adheres to hazard particulates and utilizes gravity to bring down the threat material. The spray comprises droplets of a specific size and concentration, enhanced with an applied electrostatic field. The concept for the system was adapted from coal mining practices, which employed liquid sprayers to decrease the amount of inhalable soot.
The tests occurred in a bustling environment, requiring the team to undergo training on MTA protocols related to track safety and public interaction.
“We endured long and oftentimes quite messy days,” remarks Jason Han of the Counter–WMD Systems Group, who gathered measurements in the tunnels and analyzed the data. “We all donned bright orange contractor safety vests, which led people to think we were official MTA employees. We frequently had individuals approach us asking for directions!”
Occasionally, challenges such as power failures or database glitches could hinder data collection.
“We quickly realized that we needed to capture daily data backups and maintain a constantly updated master list of unique sensor identifiers and their locations,” says fellow team member Cassie Smith. “We devised workflows and wrote scripts to automate the process, which ensured successful data capture and attribution for the sensors.”
The team collaborated closely with the MTA to ensure their testing and data collection proceeded smoothly. “The MTA was instrumental in helping us maintain the test environment, doing as much as they could in our physical absence,” Vian states.
Engaging with industry
Another vital component of the program was to connect with the broader chemical and biological industrial community to request their sensors for testing. These collaborations helped to lower the costs for DHS to incorporate new sensing technologies into the project, and in return, participants benefited from a testing and data collection opportunity in the challenging NYC subway environment.
Ultimately, the team utilized 16 different sensors, each with varying levels of maturity, which operated through diverse methods, such as ultraviolet laser–induced fluorescence, polymerase chain reaction, and long-wave infrared spectrometry.
“The partners appreciated the unique data they obtained and the chance to work with the MTA while experiencing an environment and customer base that they may not have anticipated previously,” Vian notes.
The testing phase concluded in 2024, and the final report has been submitted to the DHS. The MTA will leverage this report to enhance their PROTECT chemical detection system (originally created by Argonne National Laboratory) from Grand Central Station to adjacent stations. They aim to complete this task by 2026.
“The significance of this program cannot be overstated. This collaboration with DHS and MIT Lincoln Laboratory has led to the identification of the most appropriate systems for the MTA’s distinctive operational environment,” declares Michael Gemelli, director of chemical, biological, radiological, and nuclear/WMD detection and mitigation at the New York MTA.
“Other transit authorities can utilize these findings to initiate the development of effective chemical and biological defense systems tailored to their own specific environments and threat priorities,” adds Benjamin Ervin, leader of Lincoln Laboratory’s Counter–WMD Systems Group. “However, specific testing and evaluation within the operational environment of interest is always advised to ensure that defense system objectives are achieved.”
Creating these types of decision-making reports for airborne chemical and biological sensing has been integral to Lincoln Laboratory’s mission since the mid-1990s. The laboratory also played a key role in establishing priorities in the field when DHS was being formed in the early 2000s.
Beyond this research, Lincoln Laboratory is spearheading several additional projects aimed at predicting the impacts of novel chemical and biological threats across various domains — military, space, agriculture, health, and more — and on prototyping rapid, autonomous, high-confidence biological identification capabilities for domestic purposes to provide actionable evidence of hazardous environments.