The first step is to observe obvious conditions, such as puddles around the building after a storm, condensation on window glass during cold weather, cracks in plaster that appear in winter and disappear in summer, and the smell of musty odors during hot, humid weather. Monitoring, in a formal sense, is a series of surveys done in a planned fashion in order to assemble a more complete view of existing conditions through time. The use of instruments to document conditions and detect changes too subtle for human observation can be part of the monitoring process.
Instrumentation can indicate changes in relative or absolute measurements.
Measurements taken during a monitoring project are usually most useful as relative readings. They indicate if a condition has changed for the better or worse from a previous reading, and if the change can be tagged to an event. Monitoring instruments that automatically take readings provide ongoing observation, even when a person is not on site. The key is to be able to translate the information from the collected data and relate it to a desired mitigation program. By comparing readings from a baseline number over a period of time, the drying out of a wall or the stabilization of a climate control system can be charted.