Rescue Squad 3 is the heavy rescue apparatus assigned to Firehouse 51. Equipped with specialised tools for heavy rescue, it responds to all working fires and calls requiring technical rescue. Squad is staffed by 4-5 firefighters.
- Kelly Severide (Lieutenant)
- Tony Ferraris (Driver/Engineer)
- Capp (Firefighter)
- Joe Cruz (Firefighter)
- Jason Kannell (Firefighter)
- Jose Vargas - Dismissed on medical grounds after inhaling toxic fumes.
- Kevin Hadley - Dismissed for breach of conduct due to racial harassment.
- Jeff Clarke - Promoted to lieutenant and transferred to Firehouse 25.
- Rick Newhouse - Transferred to an unknown firehouse.
- Peter Mills - Transferred to Ambulance 61 for medical reasons, then transferred back but later resigned from the Chicago Fire Department to move to North Carolina with his family.
- Scott Rice - Resigned as he was a single father and was too scared to perform his duties for fear of leaving his child without a mother or father.
- Dallas Patterson - Promoted to Battalion Chief and transferred to Firehouse 90.