Steps to work on Firebase:
1. Connect your app to Firebase. If you haven't already, add Firebase to your Android project.
2. Add the Real-time Database to your app.
3. Configure Real-time Database Rules.
4. Write to your database.
5. Read from your database.
6. Optional: Configure ProGuard.
7. Prepare for Launch. (Next Steps...)
It really depends on the area that they are based in. The country and rural areas are called only when needed. The larger cities usually work 12 hours a day. If they are short handed the shifts could be longer. The only sure way to find out is to go to the fire house closest to you and ask. Most places will be glad to answer all your questions. Not be afraid to ask.
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