will the same model number fit on the old bracket on the ceiling which is 10 years old.

Thank you for your question. Generally, new alarms will not be compatible with old mounting brackets. We recommend replacing your mounting bracket when you get a new alarm: 1.Remove your old alarm. 2.Unscrew the screws of the old mounting bracket about halfway out. 3.Slide the old mounting bracket off the wall or ceiling. 4.Insert the new bracket and tighten the screws to secure it. Note: Screw hole locations vary between detector models, especially if the alarm you want to replace is battery-powered or 10+ years old. Sometimes, you may need to drill new screw holes. If you have any additional questions or concerns, please don’t hesitate to reach out to us at First Alert at 1 (800)-323-9005.