Deliberate mistake: Before the gas explodes in the sewer, you can see the base of the Davy lamp glow red. Except that in real life this doesn't happen; the flame simply turns blue and grows taller in the presence of gas. This was probably done to make the scene more dramatic, though.
Deliberate mistake: When the appliance crashes into the drunk driver's car and flips over, water is seen spilling out of the top of the appliance. This appliance was specially designed to flip over by mounting the water tank at the top, to make it unstable enough to tip over.