Infrared Imaging is not an x-ray and does not emit anything dangerous into the environment! IR, also known as Thermal Imaging reads the energy that is being released by the objects around us.
We use the Infrared in mould inspections to help us find hidden spots of moisture. We do this by finding areas with differences in temperature. As the water and air in a wall will take a different amount of time to adjust to the outside temperature, we use this difference to find moisture.
The IR camera is also a good tool for finding plumbing issues as it can help track hot and cold pipes and any leaks they may have.
Heating system in a commercial building.
Infrared clearly shows the path of a leak from a 3rd floor washing machine. This was completely hidden within the wall.