Carbon monoxide is a colourless, odourless and tasteless poisonous gas with a density similar to air. It therefore spreads rather slowly in the room. In technical jargon, the term carbon monoxide or carbon monooxide is more commonly used. This chemical compound of carbon and oxygen with the structural formula CO is a colourless, odourless and tasteless toxic gas and therefore particularly dangerous. When you are asleep, you do not notice the gas and can suffocate. Carbon monoxide has a similar density to air, so it spreads very slowly through the room. Since it is slightly lighter than air, it still rises slowly. It is also flammable and burns with oxygen with a blue flame. The particle concentration or the proportion of carbon monoxide is indicated with the English term ppm (parts per million). The millionth part, just as a percentage is the hundredth part of something. 50 ppm thus corresponds to a concentration of 0.005 % of the room air.