ENPreventive conservation is an important part of the entire conservation process. It includes the care of the museum objects in storage rooms and climate control. Air temperature and relative humidity in the storage rooms of the National Museum of Lithuania are monitored either visually, or with special loggers with further processing of the data on a PC. The first way is not precise enough, while the second one enables to carry out all-round monitoring and enables to avoid accidental inaccuracies. Loggers do not require any special installation; they are portable and can be connected with a PC either directly, or through a Logger Shuttle.