A fluid detecting device for detecting the presence of a substance in a fluid in an area comprising: a heating element arranged in said area, a first thermal sensor arranged adjacent to said heating element adapted to detect a temperature (T1) at said heating element, wherein said heating element is coated with a hydrophobic sorbent adapted to adsorb a substance present in said fluid in said area. The invention further relates to a method for detecting the presence of a substance in a fluid in an area.