AHUs in cleanrooms performs the following basic functions:
1. Maintain room pressure (delta p) – Areas that must remain cleaner than surrounding areas must be kept under a positive pressurization. Therefore the AHU must provide more air into the cleaner space than is mechanically removed from that same space.
2. Maintain space moisture (relative humidity) – Humidity is controlled by cooling air to dew point temperatures or by using desiccant dehumidifiers. Humidity can affect the efficacy and stability of drugs and is sometimes important to effectively mould the tablets.
3. Maintain space temperature – Temperature can affect production directly or indirectly by fostering the growth of microbial contaminants on workers.