The CULTEX® Radial Flow System (RFS) is a modular in vitro system for the homogenous exposure of cells to airborne particles at the air-liquid interface (ALI). A former prevalidation study successfully demonstrated the general applicability of the CULTEX® RFS and its transferability, stability and reproducibility. Based on these results, the methodology was optimized, validated and prediction models for acute inhalation hazards were established. Cell viability of A549 cells after ALI exposure to 20 pre-selected test substances was assessed in three independent laboratories. Cytotoxicity of test substances was compared to the respective incubator controls and used as an indicator of toxicity. Substances were considered to exert an acute inhalation hazard when viability decreased below 50% (prediction model (PM) 50%) or 75% (PM 75%) at any of three exposure doses (25, 50 or 100 μg/cm²). Results were then compared to existing in vivo data and revealed an overall concordance of 85%, with a specificity of 83% and a sensitivity of 88%. Depending on the applied PM, the withinlaboratory and between-laboratory reproducibility ranged from 90-100%.In summary, the CULTEX® RFS was proven as a transferable, reproducible and well predictive screening method for the qualitative assessment of the acute pulmonary cytotoxicity of airborne particles.