How to install battery in first alert smoke alarm

Door Window Alarm Smart Low Battery Alert 2 Mode Warning Easy Installation One-Click Power Switch

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Smoke Detector Thin Type 2 SHK48455 No Alarm and Voice Alert Set of 4 (Battery-powered, Contacts) (With Function)

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Smoke Wirelessly with Voice and AISEG SHK42422 Detector, Thin, 2-Type (Battery-Powered, Interlocked, Light) (Includes Alarm, Alert,