Clean processing areas are routinely kept at a positive pressure. Effectively maintaining this condition through maintenance and facility design -- including air-handling systems and doors that connect process areas -- presents an ongoing challenge that all plants face in providing a safe processing environment.

Though much attention is appropriately focused on the cleanliness of tools, tables, and processing equipment, airborne contaminants can’t be ignored. Fortunately, the negative pressures created by complex, finely tuned ventilation systems remove most bioaerosols before they have a chance to contaminate product as it is processed and packaged.

When all ventilation systems are working as designed and the pressure differential is balanced, clean air will flow from hygienic, pressurized pill pressing and packaging operations to ventilation ducts in areas where bioaerosol emissions are contained. Unfortunately, there are dozens of variables that can disrupt this flow and allow the airborne contaminants to find their way into the processing areas.

Entry points for outside contaminants are often found in or adjacent to various cleanroom components:

*Wind direction and velocity can create gaps between cleanroom doors and frames.

*Air intake vents may leak invisibly around fittings.

*Poorly maintained exhaust fans and air handling units (AHUs) can allow moisture and contaminants to re-enter, especially in warmer climates or warmer months of the year.