The correct way to write this is firefighter. So your answer is one word.
It is often debated to be two words, especially in some minority areas of North America. However this is incorrect, according to official English dictionaries, where it is listed as one word.
Dictionary sources:
it can take anywhere form one to two years
hydrant
Firefighting is a job about fighting fires it says it in the name
basicly its a water hose. a really big one
no it is not an one word it is of two word
Yeah okay. firefighting has been around for many years,
firefighting 101
Hipbone is one word.
I think the word "ongoing" is only one word, but it has two syllables that are two separate words.
The word "hairbrush" is typically written as one word, not two.
It is one word.
one word