A deadly toxic chlorine cloud that needs to be contained? You know the members

of 126 would volunteer to handle it, and that’s exactly what happens in TV Insider’s

exclusive sneak peek of the Oct. 7 episode of 9-1-1: Lone Star.

In the three-part finale to the Fox drama’s fifth and final season, 126 continues to deal with the emergency of a train derailment and now the aforementioned chlorine gas leak. Paul (Brian Michael Smith) and Marjan (Natacha Karam) have assembled the supplies needed to seal the leak in the train car, and Owen (Rob Lowe) is ready to put himself in the most dangerous position when he’s called to the command tent; the city has sent emergency management suits to talk to him, and they don’t ask.

Owen seeks a volunteer, and Paul and Marjan jump in immediately. “Let me be clear: This isn’t going to get you promoted to lieutenant,” he tells the pair, who are looking to replace the retiring Judd (Jim Parrack). That doesn’t change anything for either of them. Marjan ends up sealing the car, but first, they have to make sure her suit is as airtight as possible.

Owen, in the command tent, warns Marjan over the radio, “Our PPE isn’t designed to withstand chlorine gas. It’s going to leak,” he yells. “It’s going to get too intense, we have to abort, are we clear?” Watch the full trailer above for more—including how bad things go with the patch job.

Also appearing in “Cl2,” Owen names the station’s new lieutenant as Judd finds a way forward.

When it comes to this choice that Owen has to make, which he struggles with, “now that [he’s] so used to people leaving him, he’s afraid that at the end of the day, whoever he doesn’t choose might end up leaving the fire station. And so he’s just paralyzed. And so we use this train derailment to play out this play,” co-producer Rashad Raisani told us before the season.

Who do you think will be the next lieutenant? Let us know in the comments below.