Smoke & CO2 Alarms Smoke Alarms Masseys stock a wide range of smoke alarms. CO2 Alarms Masseys have a range of battery CO2 alarms as well as the patch detectors Featured products from our Smoke Alarms and CO2 Alarms category First Alert Basic Smoke Alarm £9.99 First Alert Carbon Monoxide (CO2) Alarm £24.99 Sylglas Carbon Monoxide Colour Sensor Detector £6.99