Necesitas un extinguidor (extintor) de incendios cuando hay un incendio en la cocina.
"There is fire..." was also accepted. I do know that some spanish words require the prefix while others do not (el almuerzo = "the lunch" or simply "lunch"). And some languages do not require a prefix at all. The exact same word is used to mean " boy", "a boy", or " the boy". Unfortunately, I have not yet mastered this rule.