On the call where Firehouse 51 went to the residence with the Bounce House & power lines down, Kelly Severide tells the father father "he needs to move back away from the bounce house slowly dragging your feet".
Thought this to be odd at first. But, this is actually done for safety as taken a step under the ground juiced with 200 to 300 amps generally is the lines of household voltage in the US, taken a step in this situation would be waiting to get hit by lighting.
In this episode Will Halstead Nick Gehlfuss is portrayed as being a trauma surgeon. Two weeks after this episode aired Chicago Med (2015) began. In that show the line between ER doctors and trauma surgeons are more appropriately portrayed.