The information on actual corrosivity of the environment is crucial for efficient corrosion protection since it enables operators to take immediate counter measures against accelerating corrosion, decreasing thereby the corrosion costs. Atmospheric corrosion sensors have been developed to provide continuous measurement of the corrosion rate of steel, zinc, copper, and nickel in air. The measurement method is based on the increasing electrical resistance of a measuring element made of the material concerned as its cross sectional area diminishes due to corrosion. Data on the sensor corrosion rate are available any time without the need to retract the logger from the exposure site. They can be downloaded through the General Packet Radio Service (GPRS) connection or by means of a non-contact inductive reading. The electronic logger has dimensions of 100×65×37 mm and the weight is about 180 grams. Therefore, the logger can be placed virtually anywhere. The lifetime of the monitoring system in medium-corrosive environments is designed to be 2 years with full autonomy. Metal sensors are available at several thicknesses of metal tracks according to the anticipated level of air corrosivity and required sensitivity of measurement. Sensitivity of the corrosion measurement varies from 1 to 10 nm depending on the type and thickness of the sensor. Changes in the air corrosivity can be usually detected within several hours or even tens of minutes.