Answer
In the Name of Allah, Most Gracious, Most Merciful.
All praise and thanks are due to Allah, and peace and blessings be upon His Messenger.
In this fatwa:
Firefighting is an essential service; it helps save lives and protect houses and properties which are fundamental objectives of the Shariah. If you feel you could get the training to serve as a firefighter, it would be a great service.
In responding to your question, Sheikh Ahmad Kutty, a senior lecturer and an Islamic scholar at the Islamic Institute of Toronto, Ontario, Canada, states:
Saving lives and protecting properties in Islam
Firefighting is an essential service; it helps save lives and protect houses and properties. Saving lives and protecting properties are fundamental objectives of the Shariah, so there is no doubt it falls under the category of fard kifayah or collective or community obligations. Fard Kifayah, as defined by scholars, is an essential duty, so every community should have persons who are trained in it and are ready to respond in case of an emergency or need.
Is Being a Firefighter Haram?
So, if you feel you could get the training to serve as a firefighter, it would be a great service. It is not different from any other services such as policing, serving in the army or health personnel who are trained to treat those with infectious diseases, etc.
Their services may often lead to encounters or situations endangering their own lives; that does not render it as haram. How can it be when we know that no community can dispense with such vital services? That is the reason Islam considers them as collective obligations. If the community neglects it, all of the members will be guilty in the sight of Allah.
The concern you have about passive suicide does not apply here: that would be the case only if you jump into the fire by risking your life. Firefighters are trained to take all the necessary safeguards to save themselves and others while doing their job.
Almighty Allah knows best.