If you want to complete the Fire Chief achievement in Bitlife, you will need to become a firefighter in the game and work your way up to the rank of Fire Chief.
That said, start by searching the jobs tab for the starting job firefighter and applying to it. You may need to reload or age up before the job shows up. When it does apply, and you should get accepted, as long as you have a high school education and good health, athletics, and happiness stats.
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Once accepted, you will need to work hard via the work harder option under jobs and have good relations with your higher-ups. You can get good relations and even become friends with them by hanging or giving gifts. We also highly recommend doing this, as if you have a low relationship with someone like your supervisor, it will be harder to get promoted.
That being said, make sure to work hard every year, and you should find yourself climbing the ranks in no time. You will also need to start at a firefighter and then work your way up through the following ranks ending with Fire Chief.
- Fire equipment operator
- Battalion Chief
- Assistant Chief
- Fire Chief
For more on Bitlife, check out both How to increase your notoriety in the Mafia in BitLife and How to join the Mob in Bitlife – Bitlife Mafia guide