In this study, binary powder blends of acetaminophen (ACAM) and α-lactose monohydrate (LM) at different mixing ratios, with fine, medium-size, and coarse particles are investigated with a new two-chamber setup (TCS) to assess dustiness. The TCS consists of an emission and a detection chamber, allowing plain diffusive or convective particle transport. The aim is to compare the diffusive transport of ACAM with binary blends of ACAM and LM at different particle sizes and similar apparent density. Fine ACAM exhibits significantly higher dust emissions compared to medium and coarse ACAM. With increasing LM portion in the blends, ACAM dust emissions decrease. The blend of fine ACAM and coarse LM shows the highest dust emission, while the blend of coarse ACAM and fine LM reveals the lowest emissions. The TCS offers precise, reproducible measurements with good repeatability, making it beneficial for laboratory and industrial applications, even with small powder quantities.