Nic De Foc
"Night of Fire". Usually the castillo lasts for 10-15 minutes. The Nic de Foc is the highlight of the Fallas fireworks...it is extra special, extra visual, extra inventive and extra amazing. It goes on for 25-30 minutes. Don't miss it and do pick a good spot early...once it starts the whole city will move towards a good spot and huge avenues will become totally impassable.
You will also come across something called borrachos. These are tubes which, once ignited, move around in frantic thrusts, with a long tail of sparks coming out of them. They can look very scary, thrown into the middle of the crowd (and this does happen often...otherwise it wouldn't be funny for those who throw them) but they don't appear to be very harmful in reality.
Try to keep your hands free and look around. If you see a petard landing next to you...it is like something from a war movie with grenades. You have a second to close your ears or your ears with start ringing. Take care of your ears, those petards are no Christmas cracker. They are the reason so many locals don't stay in Valencia for the Fallas and so many others are hearing impaired.
It goes without saying that if you have a serious problem with sudden explosions, such as risk of heart attack, you should not come to the Fallas.