Jesse Spencer Jesse Spencer

Warning: Jesse Spencer may play a firefighter on TV, but in case of an emergency, it's probably best to call in the real guys.

"I failed. I killed the [dummy] baby," Spencer tells of one of his recent practice runs at the Chicago Fire Academy. "I didn't find the dummy baby on the top bunk because I didn't know there was a top bunk and I led all my firefighters into a broom closet instead of an exit."

The run-through is just one of several types of training Spencer has had to go through to gear up for the part of Chicago firefighter Lt. Matthew Casey on Dick Wolf's new drama, Chicago Fire, which premieres Wednesday at 10/9c on NBC. The hour-long ensemble series follows the lives of the firefighters and paramedics working at Chicago Firehouse 51.

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After logging eight seasons as Dr. Robert Chase on House, Spencer says it was the stunts in particular that drew him to Chicago Fire. "That stuff excites me. On House for eight years, I've been doing medical jargon and wearing lab coats, so it was good to be able to do something much more hands-on," he says. "I surf, I've done free-diving and I like a bit of adrenaline, so that was really appealing to me."

Spencer returns to TV just five months after hanging up his stethoscope. "I went on a surf trip to Indonesia, so a month roughing it out there was more than enough. Coming back into it, there have been times where I have gone, 'What the hell am I doing?' It's much more grueling work than House was. House was such a finely tuned machine and this is new and we're still finding the characters and finding the feel of the show and the tone of the show," he says.  "But there's something about getting your hands dirty and being a part of the team that's just been invigorating."

"Getting your hands dirty" seems like an understatement considering the sheer number of fire sequences on the show thus far. "I didn't think there were going to be as many as there are actually," he says. "I did do one today where this door is burning down. ... They covered me in the fireproof gel. I couldn't even feel it. It was crazy. The stuntmen would yell at me, because apparently the fire was licking my face."

Check out photos from Chicago Fire

Although there are, thankfully, stunt doubles on hand to film the more dangerous scenes, Spencer and the rest of the cast have also been doing ride-alongs, gear drills and real-life runs into the burn room, like the one Spencer failed, since production started. The show also has a fire consultant on staff, who in turn has brought other real-life firefighters on to the set. "They're constantly around, which is a valuable source of information, because if we've got questions, you literally just turn around and ask the closest firefighter what's up," he says. "We still shoot at the real firehouse once a week and there are other firefighters there, so it's pretty authentic surroundings for us."

After moving to the Windy City to shoot Chicago Fire, Spencer said he and the cast have logged plenty of hours with the firefighters off set as well. "We've really got a rapport because we spend so much time together. We hang out on weekends and we hang out with the firefighters, so it's a different energy and a different scene and that's quite invigorating," he says.

Spencer says living in Chicago has also helped him adjust to using an American accent — a first for the Australian native whose House alter ego was also from Down Under. "Eamonn Walker, who's our chief on the show, is English as well, so we commiserate on how difficult it is sometimes to change everything," Spencer says. "In terms of TV shooting, there's just not really a lot of time, so you just really do it on the fly."

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On Chicago Fire, Spencer's American-born character, Casey, is estranged from both his wife (Battleground's Teri Reeves) and a friend and colleague (Vampire Diaries' Taylor Kinney) after the death of one of his men in the line of duty.  Spencer says that the character appealed to him because Casey is far from the antihero trend made popular largely thanks to House's acerbic titular character. "Everyone's got a psychological problem or a bad streak or they're drug-addicted or this or that, and this felt like a real stand-up American guy who wants to have a family and he wants things to go smoothly," he says. "These firefighters — they're great, open, honest, genuine guys, so I felt more that I was playing a real guy than some sort of TV-concocted trick to get people hooked."

Unlike House, and what may be TV's most famous firefighter drama in recent years, FX's Rescue Me, Spencer says Chicago Fire is far less bleak. "Our show is more of an inspirational, optimistic view of firefighters. We do delve into all sorts of issues, but it doesn't get bogged down in the psychological element of it. It's an hour of entertainment," he says. "You see their lives outside of the firehouse probably just as much as you do in. It's an ensemble, so we follow these characters not just into fires, but into the bedroom."

Chicago Fire premieres Wednesday at 10/9c on NBC.