Product image from current catalog dataProduct overview
First Alert SMI100: What to Know
A substitution note upfront: our original candidate for this slot, the First Alert SA303CN3, is listed as discontinued on First Alert's own store, with the retailer explicitly directing shoppers to the SMI100 as its replacement. We're describing that manufacturer-recommended successor here rather than a dead product.
Per First Alert's own product page, the SMI100 is an 8th-generation smoke alarm using an ionization sensor, which the company states reliably detects fast-flaming fires. It runs on a single 9V alkaline battery (not included per the listing) rather than a sealed long-life cell, meaning periodic battery replacement is part of normal maintenance, offset by a lower upfront price than the sealed-battery combo units in this guide.
First Alert's spec sheet lists an 85 decibel alarm at 10 feet, UL 217 compliance, a front-access battery compartment, and a test/silence button. The company states this model uses the same "Precision Detection" sensing technology as its newer alarms, aimed at better distinguishing cooking smoke from genuine fire smoke than older-generation sensors.
Key Listed Features
Ionization sensor tuned for fast-flaming fire detection
Precision Detection sensing to reduce cooking nuisance alarms
Single 9V battery with front-access compartment
UL 217 compliant, 85dB alarm at 10 feet, 10-year limited warranty
