Factual error: Roy uses the defibrillator paddles on the electrocuted man twice, then after each defib Roy lifts the paddles off the patient's chest and they look at the EKG monitor, which shows flatlining the first time and a heartbeat the second time. Problem is, it's impossible for the EKG monitor to show anything at all. Either the defib paddles must be in contact with patient's body for the “quick-look” to determine the rhythm, which they were not, or the ECG electrode discs must be on his chest connecting him to the EKG monitor, and they were not.
Other mistake: When Station 51 is at the scene with the electrocuted man, he's dangling from a rope below the second stem of the letter H, in the large sign which reads "HOTEL", above the striped awning. In the shots from above the sign, looking directly down as they set up the ladder, we can see the letter H and the awning, but the dangling man is simply not there in the shots from this perspective, even though we should be able to see him.
Other mistake: During the fire at the chemical plant, when Captain Stanley and Roy find the missing man and carry him out, the subtitles read that Johnny says "All right, grab his feet," when in fact it's Captain Stanley who says that - Johnny's not even in the same room with them.
Continuity mistake: While the boy who has cyanide poisoning is in the ER, Dixie looks through his clothing and finds carved peach pits, and when she directs Brackett's attention to all the carved pits, the items change when it cuts to the closeup. Additionally, that closeup starts out being farther, and we can see that Dixie is not beside the table before it zooms in.
Continuity mistake: When Station 51 is being dispatched to the fire and explosion at Martell Industries, the other companies called are Station 36 and Engine 14, but we see Engine 236 at the scene even though they were not called. This is before Captain Stanley asks dispatch for the second alarm.
Continuity mistake: During the fire at Martell Industries, when Roy and Johnny make a mad dash out of the building before the explosions, and midway Roy's helmet falls to the ground as he keeps running, but in the next shot when he and Johnny reach the engine and dive to the ground, the helmet is hanging around Roy's neck.
Visible crew/equipment: When John and Roy help the driver out of the overturned armored truck, the bulging outline of the mic transmitter is visible on the left side of the driver's shirt, and when Roy's arm is around the man's waist, Roy even puts his palm over the mic transmitter as he bends to pickup the man's gun.
Continuity mistake: During the fire at the chemical plant, the distinctively marked SCBA tanks that Captain Stanley, Johnny and Roy are wearing, when they're searching for the missing man, change when they're inside and then finally exit. Note the different stickers, or lack of stickers, on their tanks.