Other forms: firefighters
A firefighter is someone whose job involves investigating and putting out accidental blazes. If your gas stove ignites a towel and you can't put out the flames, call the firefighters!
The word fireman is older than firefighter, which first appeared in the late 19th century, and for a long time it was much more commonly used. These days, it's more accurate to use firefighter, since men and women both work for fire departments battling fires. Also, the word perfectly describes the job itself, fighting dangerous fires.