The first unit operation is the introduction of the various ingredients and raw materials into the manufacturing process. This starts with accurately weighing the APIs, excipients, fillers, and miscellaneous materials, and then dispensing them into the process vessel. Handling powders typically produces dust, so ingredient dispensing must occur in a controlled and contained environment. This may include local exhaust ventilation (LEV) enclosures, downflow booths, isolators, or other containment and process control devices.