There are different types of fire detectors: smoke detectors, heat detectors and CO detectors. Each one has its own distinct function. We explain the difference here.
Smoke detectors only detect smoke itself: by means of an optical measuring system, the detector continuously registers whether and how many smoke particles are in the air. If there are too many, the detector will sound an alarm. Since smoke always rises, it is important to hang a smoke alarms as high as possible, preferably on the ceiling. Only if you have a pyramidal roof, you should install the detector 30cm lower than the ridge of the roof because stagnant air can prevent smoke from rising.
Heat detectors do not detect smoke, but continuously measure the temperature of the room. They sound an alarm if the temperature exceeds a certain limit. Heat detectors are very useful in places where smoke detectors would give too many false alarms, especially in places where a lot of (water) vapor or other gases may be present, such as in the kitchen, bathroom and garage.
CO detectors continuously measure the amount of carbon monoxide, or CO, in the room. Carbon monoxide is a very dangerous gas. It spreads evenly through the air if it doesn't burn up properly and there's not enough oxygen to form CO2. It's odourless and invisible. CO detectors are therefore essential in homes that are heated by a combustion boiler.
Gas detectors do not detect carbon monoxide, but they do detect other gases. They measure the presence of natural gas, butane, propane and LPG. Depending on the type of gas you want to detected, you can place the detector low to the ground (butane and propane) or close to the ceiling (natural gas and LPG).