They are usually connected to a fire alarm that sets off an audible warning when triggered, or to the automatic sprinkler system if you happen to have one installed in your house. In countless instances, smoke detectors have given ample time for home or office occupants to escape before the fires could do greater damage. They have certainly saved lives. Having a smoke detector warns a house occupant early on that something is burning and needs to be put out. Now, the saving part depends on whether or not you have the tools and equipment to put the fire out or whether your fire department is quick to respond to such an alarm. You also have to be alert enough to either try to put out the fire yourself or call the fire department immediately. Smoke detectors are made with different kinds of sensors that detect excessive smoke when it is present and gives out the alarm, or triggers the automatic fire control system. It is best that homeowners are able to see the difference among these different types and see how they work, before deciding on which ones to buy and install in the house. The type of sensor installed in a smoke detector may also dictate the price range, since there are sensors that have more expensive components than those of the other types. Among the types of sensors presently used by several manufacturers of smoke detectors are the ionization type, the optic sensor – also called photo electric sensor, the air sampling sensor, and combination type sensors. A smoke detector with an ionization type sensor uses what is called radio isotopes that produce ionization in the air.