Notifier 400 Series plug-in smoke detectors are designed to meet the performance criteria designated by UL/ULC. The ion units have a sensing chamber sealed from back pressure air flow, dirt, and insects. This chamber is protected by a fine mesh screen which can be cleaned or replaced. Additional key features include a recessed mounting option, interchangeable ion, thermal detectors, a variety of mounting bases, and a full line of optional accessories. Avalible in the 1451 Ionization detector, or the 2451 Photoelectric detector.