The i4 Series combination CO/photoelectric smoke detectors simplify two technologies into one device, requiring less wiring and fewer backboxes than two separate devices. The i4 Series is compatible with the i3 series, so an attractive CO monitoring solution can easily be retrofitted into existing i3 installations. The i4 Series CO cell can be easily replaced at end-of-life, resulting in a much lower life cost than having to replace the entire detector. Installers can pre-wire the i4 Series plug-in base, while a large wire entry port and in-line terminals provide ample room for neatly routing wiring. The base accommodates several back box options and also direct mounts using drywall anchors. The i4head plugs into the base with a simple Stop-Drop N Lock action. When the CO cell reaches end of life, it can be easily replaced in the field without a tool. With the help of the module, the i4 Series detectors transmit distinct CO and smoke signals, allowing appropriate response from the central monitoring station. Intelligent features, such as drift compensation and smoothing algorithms, reduce nuisance alarms. The i4 Series LEDs enable instant inspection of detector status signaling normal/standby condition, alarm condition, maintenance/trouble condition or functional test mode. 2-wire devices allow loop testing via the EZ Walk feature where wiring can easily be verified by checking the LED status at each detector. Smoke sensitivity can be easily measured using the wireless SENS-RDR device. CO cell functionality can also be quickly validated in the field with canned CO per NFPA 720: 2009 requirements using the detector's RealTest functionality.