Pharmaceutical manufacturing assembles every element of a deflagration into single pieces of process equipment, deliberately, because that is what the process requires. A fluid bed dryer suspends fine powder in a heated air stream. If the granulation used a flammable solvent, that solvent is evaporating into the same air stream. The result is a vessel containing an explosible dust cloud, flammable vapor, elevated temperature, and high-velocity airflow generating electrostatic charge, all at once.
Active pharmaceutical ingredients and excipients are typically fine, dry, low-moisture powders, which is close to worst case for explosibility. Particle size drives the severity of a dust deflagration, and pharmaceutical processing specifically works to reduce particle size for dissolution and bioavailability reasons. Milling, granulating, drying, blending, compressing, and coating each generate suspended dust, and the connected equipment provides propagation paths between them.
What makes this industry distinct in practice is that the facility cannot be freely modified. Cleanroom construction has validated integrity that penetrations compromise. Process equipment and utilities are qualified under GMP, so a change to a vessel or its controls triggers revalidation. Fire protection modifications that would be routine in a general industrial plant become change control projects with documentation requirements attached. Protection needs to be designed correctly the first time, because retrofitting it is disproportionately expensive here.