Equip yourself with fire extinguishers and sprinklers, too, if necessary. Photo Electric or Optical Sensors They are triggered by smoke disturbing an existing beam of light inside the detector. When smoke is not present, the beam from a light source inside the device travels in a straight line to a detector, but when smoke particles enter, some of the light is scattered and triggers the electrical circuit that sounds the alarm. Air Sampling Detectors These have sensors that are capable of detecting microscopic smoke particles in the air. They actually draw air into the detector and passes it into minute pipes that lead to a laser optical device that has the capability to detect minute particles of combustion. When the laser detects the unusual content, it triggers the alarm. Combination Type Detectors It use both ionization and optical sensors, as mandated by some states. Ionization detectors tend to react slower, and may not warn people inside the house or commercial buildings adequately enough to be able to make it to the exit. So fire departments and legislative bodies recommended installing photo electric smoke detectors, or combination type detectors. The other feature that one may consider in a smoke detector is its gas detection capability. Incorporated in many of the newer models are carbon monoxide and carbon dioxide sensors that trigger an alarm when there is a high level of these gases present in the air.