Accurate particle assessment of spacecrafts and cleanrooms during the AIT (Assembly, Integration and Testing) activities is key to guarantee both mission lifetime and performance. The Particle Fall Out (PFO) photometer from Ingenious System BV is still widely used in space industry, and it has proved to be a reliable method no dependent on the physical properties of the contaminating particles, such as the shape or the color. However, this system shows limitations in terms of data output (only obscuration factor) and uses witness plates which are neither transport proof nor suitable for detailed microscopic analysis under electronic microscope (e.g., SEM-EDX). Alternative equipment is used in other sectors in which particle fall out is also of particular concern, such as automotive, semiconductor, and optics industries. The new instruments and methods produce extended data outputs, including statistical information on the size distribution of the particles, they have the necessary reliability in the transport between area assessed and analysis laboratory, and they are compatible with electronic microscopy methods coupled with elemental composition mapping and analysis for the investigation of contamination anomalies. For optical equipment these systems can provide a more accurate straylight forecast in targeted AIT environments, thus improving optical performance predictions. Airbus Defense and Space and the European Space Agency have joined R&D efforts to define a thorough comparative study between different equipment. Pro and cons, limitations, as well as improvements for future systems will be discussed. Statistical analysis of the different outcomes provides evidence that the alternative methods are compliant with space standards and can be implemented as replacements of the established reference methods.