First Alert Slim 10-Year Maximum Protection Photoelectric Smoke and Fire Detector, White $15.29 + Free Shipping and More Options From $5.98 Shipped

Amazon has the First Alert Slim 10-Year Sealed Lithium Power Battery Maximum Protection Photoelectric Smoke and Fire Detector, White $15.29 + Free Shipping after clipping 10% coupon on product page. 

• Photoelectric Smoke Alarm
• Nuisance-resistant Technology In New Sleek Design
• 3v Sealed Lithium Power Sealed Battery
• Power Led & Alarm Indicator
• Mute/silence Button
• Complies with all current 10-year legislation in states/cities where required
• No Battery Changes for the Life of the Alarm; 3V Lithium Power Cell Included

More Options:

• Kidde i9040 Battery-Operated Ionization sensor Compact Smoke Alarm $5.98
• First Alert SA303CN3 Battery Powered Smoke Alarm w/ Silence Button $7.67 Best Choice
• First Alert SA304CN3 Smoke Alarm with Escape Light $10.99
• AmazonBasics 9 Volt Everyday Alkaline Batteries (8-Pack) $8.49 - $9.49
• Kidde KN-COB-B-LPM Carbon Monoxide Alarm $14.84

Alarm Types:

There are currently three types of smoke alarms on the market: ionization, photoelectric and combination ionization/photoelectric.

Ionization

An ionization smoke alarm contains a small amount of radioactive material. The radiation passes through an ionization chamber which is an air-filled space between two electrodes and permits a small, constant current between the electrodes. Any smoke that enters the chamber absorbs the alpha particles, which reduces the ionization and interrupts this current, setting off the alarm. This type of alarm responds best to fast raging fires.

Photoelectric

Photoelectric smoke alarms operate using a light source, a light beam collimating system and a photoelectric sensor. When smoke enters the optical chamber and crosses the path of the light beam, some light is scattered by the smoke particles, directing it at the sensor and thus activating the alarm. This type of alarm responds best to slow smoldering fires.

Combination

Combination smoke alarms feature both ionization and photoelectric technologies. Ionization smoke alarms respond faster to high energy fires, whereas photoelectric detectors respond better to low energy smoldering fires. The NFPA recommends using both smoke alarms in the home for the best protection.

Source: Grainger