First Alert Model 9120B Reviewed

first alert 9120bThis model of smoke detector is hard wired and comes with a 10 year limited warranty. It is very affordable. The 9120B is an improvement from the previous 9120 with better performance and ease of installation. This is a great choice of a smoke alarm, if you are looking to quickly detect flaming fires.

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The engineering design uses the ionization sensing technology that is very ideal at detecting flaming fires unlike photoelectric sensing technology that is most suitable for smoldering fires.

First alert smoke alarms meet UL smoke detector standards.

First Alert 9120B Features

What actually makes this model different from its predecessors? To begin with, the size and weight are almost the same with 9120. However, the First Alert 9120B comes with standard battery backup. This definitely ensures that you are covered in case of mains power outage. To replace the battery, simply slide the drawer on the sides, you do not have to un-mount the whole alarm.

Both 9120 and 9120B models have universal mounting brackets to make installation and replacements faster and easier. They also have a test or silence button tamper resistant locking pins as well as latching alarm indication. Since First alert 9120B was developed after 9120, it is more accurate and does a better job to suppress nuisance alarms.

Having compared the two First Alert models 9120 and 9120B, you should also be aware that there are newer versions of this model available in the market as well. These are SA9120BCN and SA9120BPCN. These two new models are improvements on the First Alert 9120B.

First Alert SA9120BCN Smoke Alarm Hardwire with Battery Backup


It has similar dimensions as the 9120B but slightly heavier. It is hard wired to 120V ac mains power and has a battery backup of 9V, just like the 9120B. It has the rest of the features available in 9120B but in addition this type can interconnect with up to 12 other first alert hard wired alarms.

First Alert 9120B6CP Smoke Alarm


This model is slightly heavier than SA9120BCN. It has all the features of SA9120BCN but the differentiating feature is the additional adapter plugs that are meant to make easier the replacement of smoke alarms not manufactured by First Alert.