Heat Detector

This is probably a silly question, but...

We have an old (hard wired) heat detector in our kitchen. My guess is at least 20 years old - made by Fire-Lite. Anyway, thought it would probably be a good idea to update it.

The heat detector is connected to its mounting bracket but the wire just comes out of the ceiling and around the screws of the heat detector.

Not seeking to make this molehill project into a mountain, how important would it be for me to put in a junction box to surround the wire bringing the AC? Obviously, it's a much easier job to just put in a new mounting ring into the drywall (ceiling) and wire up the detector.

Thanks for the advice...

Any time line voltage comes through a wall/ceiling/floor it needs to come into a box.

Is this a low voltage device which is part of a home security/fire alarm system?

It's just a smoke detector - 110V... nothing too special. Not adding a new one, just replacing one that is dead (but line is working)... old one just had a wire that came out of the ceiling...

Put a box in the ceiling.

I would throw a box in. The work to do so is minimal (assuming your ceiling is sheetrock).

Get an old-work ceiling box.

http://www.carlon.com/Brochures/2B1-OldWork-Low.pdf