Insight into the dust explosion hazard of pharmaceutical powders in the presence of flow aids

Coating of nanoscale flow aids is widely used in pharmaceutical applications to increase the flowability of cohesive powders. For combustible pharmaceutical active ingredients and excipients, it is unclear whether increased flowability affects the dust explosion hazard. In this work, acetaminophen (APAP) and microcrystalline cellulose (MCC) were studied with and without a coating of silica nanoparticles. A full set of explosion parameters for the pure materials and their flow-improved mixtures was determined in accordance with ASTM standards. The results show that parameters including minimum ignition temperature, minimum explosible concentration, and maximum explosion pressure were independent of powder flow properties, while the presence of flow aids led to significantly lower minimum ignition energy values for both APAP and MCC, and a slightly higher maximum rate of pressure rise for APAP. The connection between dust flowability and the dust explosion hazard is discussed with respect to these experimental results.