In several episodes, the ambulance that is often used by the paramedics has a license plate number of BN6-30L. In New York, that would be a passenger plate number, also, FDNY ambulances use official plates.
Carlos Nieto states in several episodes that he was a medic in the Marine Corps. This is impossible as the Marine Corps has no medical staff of its own. Corpsman, even when assigned to Marine units, are from the Navy Hospital Corps.
Contrary to the depiction in the show, ambulances do not operate out of firehouses and EMS has its own separate chain of command in FDNY.
At the beginning of the season two finale, Jimmy and his son, Joey are playing the Syphon Filter video game. They stop when Jimmy says that Joey killed him (in the game). However, viewing the TV screen shows that the game was in single player mode.
In several episodes, cameras and equipment attached to the police cruisers and ambulances are visible in reflecting buildings and passing car windows, as the camera view shows the cast member in the far seat of the vehicle from where the camera is mounted.
The 55th precinct building is nicknamed "Camelot" because it
is supposedly located at the intersection of King St. and Arthur St. This is impossible because while King St. is located in Manhattan, Arthur St. is in Queens.