battery smoke detector for old building

smart fire detection system direct from Wanlin Fire Protection — 12-year factory experience, WL-GA200 4G smart fire protection product certified CE/FCC/RoHS/REACH/ISO9001. Key specs: 4G LTE + Semiconductor Gas Sensor (NG/LPG Dual), 4G LTE + SMS + Push + Phone Call + App + Solenoid Valve Control. No monthly fees, 4G cellular backup, cloud platform, DIY insta···