Thermal imaging cameras do not act as X-ray machines.
Thermal imaging detects temperature at the surface of an object and displays on a screen, different colours depending on the temperature.
The results of any wall scan are highly dependent on the quality of the camera, the skill of the camera operator and whether there is a heat source (curing concrete or the sun) to heat the area being scanned.
When used to attempt to detect voids in a wall, the assumption is that a void will be a different temperature to the rest of the wall.
A thermal image scan can be effective in detecting flow and pour heights during concrete pours – the exothermic reaction in concrete provides the temperature differentials for the scan.
As most voids occur well within the wall around congested reinforcement zones, it is highly unlikely that any such voids will be detected – you may only see surface voids.
Thermal imaging camera penetration field
So don't be fooled.
Eliminate risks and air voids by using self-compacting concrete.
