The study is mainly based on a laser technique to measure in-line fouling layer thickness. This method basically involves the capturing of reflected light by a camera. During the fouling process, particles stick over the tube and a deposit layer starts building up. A video camera is mounted perpendicularly to the air flow to visualize the line formed by the laser sheet. A Laser Sheet Generator using a laser pointer as energy source was manufactured in order to create this laser sheet. A MATLAB program which compares the photos of the tube surface with and without deposition is used to determine the fouling layer thickness. The test conducted on a machined surface with steps has shown good accuracy of the technique. Previous experiments with another laser sheet source showed that the surface conditions strongly affect the reflected light. Besides, the aperture setting of the camera is another important parameter due to the modifications it can cause on the amount of light captured. In-line measurements have demonstrated that the implementation of this technique is applicable and accurate. A new test section, in order to solve the problems faced during the fouling experiments as well as a rotational device, capable to measure the deposited layer thickness circumferentially, are also presented.