Humidity and air temperature – these are those decisive factors that may significantly influence the environment and well-being in this environment. The museum data logger and humidity detector is one of a few devices from the range of humidity detectors manufactured by PCE Instruments, that helps the users to absolutely precisely and quickly find out whether the conditions in a certain room, area, facility correspond to the required standards. This data logger finds its application in many areas where fluctuations of the most important parameters like humidity level and temperature are not just a matter of comfort, but are of a paramount importance like in a museum. Not always it goes about only well-being of humans, which is for sure very important, that is why all the HVAC systems should be monitored and checked regularly. Many things which people need and use in their daily life, that are essentially important or bring esthetical pleasure, or are of historical value are in direct dependence on the conditions under which they are stored, transported or used.