Factual error: When Roy is electrocuted and falls from the roof, after Karen uses the defibrillator paddles on Roy, she lifts both paddles, looks at the EKG monitor and says "He's converted." How exactly could Karen have known that he's converted? It's impossible for the EKG monitor to show anything at all. Either the defib paddles have to be in contact with Roy's body for the "quick-look" to get a reading, which they weren't, or the ECG electrode discs have to be on Roy's chest connecting him to the EKG monitor, and they weren't. As an aside, just watching Marco having problems attaching the air mask, and quickly glancing up towards the camera frustrated, then giving up is priceless.
Revealing mistake: At the apartment complex fire, after Johnny is knocked unconscious by the explosion, when the Pasadena fireman finds him and has to lift him up, it's funny how even though Johnny's unconscious we can see that he actually helps to stand himself up, so the fireman can lift him up and carry him out.
Visible crew/equipment: When Station 10 is dispatched to the factory fire, a few shots after the closeup of 105's door that reads "fire dept deluge", there's an overhead long shot of the men using the hoses against the fires in the doorways, and a cameraman wearing blue, holding a handheld camera, is visible sitting at the back of a squad.
Other mistake: On scene at the traffic accident, when the woman and the boy with non-serious injuries are seated at the back of the ambulance, neither Roy or Johnny are going along with them to Rampart, yet Johnny puts the drug box inside the back of the ambulance with them, and the ambulance drives off. With their drug box! Captain Stanley even says that he'll advise dispatch that they're available for a run at the scene, while the guys will be looking for the dog.
Visible crew/equipment: When Roy has trouble sleeping in the middle of the night, he gets up, and when he goes to the bathroom sink, there is a fully dressed crew member whose reflection is visible in the mirror, as he moves around and looks through the door window towards the actor. Then 51's tones drop, and in the next shot we see that all the other guys of Station 51 have been lying in their beds, before getting up and putting on their turnouts.
Visible crew/equipment: At the site of the major chemical leak, after Johnny falls from the pipes and Roy lifts him up, a couple of shots later there is a medium shot of one of 105's guys on Deluge 105 pumping out water, and we can see a cameraman (filming Deluge 105's closeups that we see during this scene) holding a handheld on the right of the screen, behind the pillar.
Visible crew/equipment: Just after Herbert leaves the station in the morning, dispatch sounds the alarms, and when Roy and John are in the squad while the dispatcher begins talking, there are nice reflections of the camera, reflector screen (in the background), and crew members/cameraman who move around, that are visible on the surface of the spotlight. Additionally, the shadow of the boom/mic is perfectly visible on the windshield as it moves down.
Revealing mistake: At the start of the episode, we see Squad 51 speeding toward their destination, and when the camera cuts to the woman in front of the market, she's waving her arms to the squad somewhere in the distance. But notice that while Rosa is looking to her left and waving, we can see Squad 51's reflection in the window (with the liquor bottles), as they are parked right there, just off-screen waiting for their cue to "speedily" pull up.
Visible crew/equipment: When Station 51 arrives at the salvage yard's fire, Johnny gets out of the squad, and when he puts on his turnout coat as the camera zooms out, a dark haired crew member wearing a short sleeve white shirt is visible at the lower right corner of the screen.
Other mistake: In the interior shots of Station 51 (the studio set), when facing the rear apparatus bay door, the right wall has a door to Captain Stanley's office, a very large map, the radio receiver base station where they respond to dispatch, the kitchen doorway, and a double-door closet, that's it. However, when Station 51 is shown in the exterior shots (the real Station 127 aka 51), as either the engine or squad exits when the apparatus bay door is up, we see that the right wall has many more doors on that wall. Additionally, the opposite wall on the set has only two doors - one to locker room/bathroom, and one to the dorm, however at the real 127's, that wall has three doors - two of them are to the dorm.
Visible crew/equipment: As the camera pans to the left at the start of this episode, while everyone is asleep in the dorm upstairs, a crew member standing near the production's lighting equipment is visible between Squad 10 and the wall. Also note that the lighting equipment is gone when the guys are dispatched.