Visible crew/equipment: After the man with trichloroethylene poisoning is hosed down and loaded onto the ambulance, while Roy's on the Biophone with Rampart, John's uniform jacket is pulled open with his hands on his hips, and we can see the outline of his mic transmitter in his shirt pocket with the wires coming out of the pocket.
Continuity mistake: Responding to the elevator call, in the overhead shot Squad 51 pulls up adjacent to the street awning when Gage and DeSoto get out, but in the next ground shot the squad is 20-25 feet farther down.
Continuity mistake: When the guys are dispatched to the cardiac patient stuck in the elevator, Gage leaves the mop and bucket in the middle of the floor in the apparatus bay and rushes to the squad, but when they roll out the bay floor is clear.
Continuity mistake: At the start, Station 51 and Truck 8 are dispatched to the cardiac patient stuck in the elevator, and we even see Truck 8 roll up in front of the building in the overhead exterior shot, but in the hotel it's 127's guys with 51's.
Other mistake: At the start of shift, while John's putting the pillowcase on the pillow we hear the dispatcher say, "Boat fire, dock 61," but subtitles read, "Open fire, dock 61." Subtitles from Universal Studios 2010 DVD.
Continuity mistake: When Johnny explains to Roy how he met Cynthia, he says that he "TX'd for Kirk on B shift," and at the end of the episode we see Kirk, who traded shifts with Chet, and Kirk is even played by the same actor who played 110's Kirk, Tom Wheeler's partner in a previous episode Publicity Hound, and also in the next episode, Crash.
Continuity mistake: After being dispatched to "industrial accident at railroad yard," once they rescue the man from the train car carrying trichlorethylene, when Roy and John are standing beside Engine 51 we can see the empty red disc on the side of the engine covering the real engine company number (127), as well as the American flag sticker on the windshield. Earlier, when they were dispatched, there's no disc or sticker in the closeup of Engine 51 (played by Engine 60).
Other mistake: When Roy and John get back to the station and start discussing Cynthia, John takes a milk container out of the fridge which has orange tape covering the brand name.
Answer: It is standard practice to wet down driveways so that they stand out in a long shot.
stiiggy