Translation of "dense fog" into French

London has been brought to a halt by dense fog, which has descended overnight.

Londres est immobilisée par un brouillard épais qui s'est abattu cette nuit.

That's what we thought at first, an especially dense fog mixing with the chlorine gasses from the factories.

C'est ce que nous pensions au début, un brouillard dense rempli de chlore gazeux provenant des usines.