Gabriela Dawson
Gabriela是個充滿活力的急救人員，個性堅強，有鬥志，勇敢又熱情-這些特質讓她在工作上很順遂，但對Mattew日益增溫的愛慕，反成了一種阻礙。
Spirited medic Gabriela is strong and ambitious, fearless and passionate – qualities that serve her well at work but turn out to be stumbling blocks as she fights her growing attraction to Matthew.
Leslie Shay
Leslie 是第51消防小組的急救醫療老手，絕不說廢話，忠心耿耿，她最好的朋友Kelly正是她完全相反的類型。跟Kelly一樣，她喜歡輕鬆隨便處理浪漫關係，但是他的約會哲學只是為了掩飾前女友留給她的情感傷害。
The no-nonsense veteran paramedic of Station 51, Leslie is unwaveringly loyal and finds a male counterpart in best friend Kelly. Like him, she prefers to keep her romantic relationships on the casual side, but her philosophy on dating barely disguises the emotional scars left behind by her ex-girlfriend.
Peter Mills
出身自救火兄弟世家，在第51號消防小組的弟兄因公殉職，需替補成員遺缺之際，Peter立即加入。為了融入團隊，他必須努力證明他的能力，而現在面臨一個困難的抉擇: 繼續與Mattew同車，或者接受訓練，加入Kelly的急救小組。
Descending from a multi-generational family of firefighters, Peter joins Station 51 immediately after their loss of a member. While he quickly endears himself to the team, he must work hard to prove himself and a difficult decision awaits him: to remain on Matthew’s truck, or train to ride alongside Kelly’s rescue squad.
Kelly Severide
Kelly是第3急救小組隊長，個性莽撞，需要克服自身的缺點，常常會讓自己的人際關係陷入困境。如同家人的隊友，也不知道他受脊椎問題所苦-連Leslie-他的摯友兼室友，也被瞞在鼓裡。
The brash leader of Rescue Squad 3, Kelly battles many personal demons and has a tendency to land in hot water with his relationships. While his squad is his family, he hides from them the crushing spinal pain that is afflicting him – even his best friend and roommate, Leslie, is kept in the dark.
Matthew Casey
Matthew是81號消防車的隊長，個性強悍又務實，充滿經驗，與Kelly Severid之間的嫌隙，讓他處理罹難救火兄弟事件更加的棘手。他的私人生活也不順遂，他與未婚妻的關係開始出現問題， 因而在急救醫療同事Gabriela的身上找到慰藉。
The strong, pragmatic leader of Truck 81, Matthew’s efforts to deal with the death of one of their own is complicated by his rift with Kelly Severide. Things aren’t too rosy on the home front either when his relationship with his fiancée starts to unravel and he finds a confidant in paramedic Gabriela.