By Lynette Cornell

Scientists are passing gas through Boston’s transit system this week to study how toxic chemicals could spread in the event of a terrorist attack. The study, which was commissioned by the Department of Homeland Security (DHS), is a summertime version of a similar study conducted in December. Because temperatures can affect the behavior of gases, the scientists are comparing the results of both studies to see if the countermeasures proposed after the December study would be effective in summer conditions, according to a press release on the Massachusetts Bay Transportation Authority website.

Starting last Friday, scientists from international laboratories have been releasing invisible and innocuous sulfur hexafluoride and perfluorocarbon tracer gases into the the underground system and using sensors to track the gases’ progress through the underground tunnels. According to the MBTA press release, the gases are odorless (although it’s doubtful that commuters would notice if they were, given the usual train car smells). Scientists, positioned at more than 20 stations throughout the system, are using electronic air sampling devices to measure air quality and particle levels.

The MBTA is notable for being the nation’s oldest subway system and, given its age, it’s no surprise that the DHS has pointed out the transit system’s poorly ventilated tunnels, which would make a tempting target for would-be biological terrorists. So, it’s exciting to see technology making an entrance into the aging infrastructure, the first tunnels of which opened in 1897. To give perspective, that was the first year the term “computer” was used to describe a calculating machine. Perhaps bringing in some new technology to assist in updating the safety of the rail system would be a good idea.

As a regular patron of the loved-yet-hated MBTA, I’m interested to see what the study finds and learning how much time I’ll have left to breathe if someone does decide to launch an airborne toxin attack. I’m also interested to see what the MBTA will do to solve this problem. I’m predicting that to avoid the cost of a full-blown ventilation renovation project, they’ll install drop-down oxygen masks like those on airplanes. And if people’s willingness to offer up a seat is any indication of your chances of getting one of those air masks, well, you might want to hold your breath.