Focs (what a remarkable coincidence) is based on the Catalan for "fires" e.g "tens foc" means do you have a light for my cigarette.

In Manresa they have a "Correfoc" literally "running fire" with thousands in the streets and hundreds of thousands of fireworks being let off, mostly it seems at once. All the fireworks let off would probably be illegal in the UK, at least without supervision they would be.

These are fireworks.......