Breakdown of Il vigile del fuoco disattiva il rilevatore di fumo.
Questions & Answers about Il vigile del fuoco disattiva il rilevatore di fumo.
It can be both, depending on context.
In this sentence, il vigile del fuoco most naturally means the firefighter or a firefighter, depending on the situation. Italian often uses the definite article il where English might sometimes use a or just a role name.
Also, vigile del fuoco is the standard Italian term for firefighter. It is a fixed expression, not something you usually translate word by word in normal use.