Atmospheric gases namely oxygen and carbon dioxide are the main sources for microbial growth. Oxygen has a more significant effect on microbial growth. Dust particles in the outside air are the main carriers for soil organisms like Clostridium, yeast, molds, etc. Indoor air also contains bacteria like streptococcus and staphylococcus species on cloths or human skins. These microorganisms are also present in droplets expelled from the mouth and respiratory tract of humans while talking, sneezing, and coughing. Microorganisms free from dust particles are found in indoor and outdoor air. The damp atmosphere contains fewer microorganisms than the dry atmosphere because the contaminants are carried down by the moisture droplets. Hence, the cold stored air is usually free from microorganisms.
Method of Prevention:
- Maintain the air humidity level inside the clean room.
- Operators should move as much as possible inside the clean room.
- Aseptic rooms are maintained at higher differential air pressures than adjacent controlled areas.
- Air filtration and air change rates should be set to ensure that the defined clean room class is attained.
- Air flow over critical areas should be uni-directional (laminar flow) at a velocity sufficient to sweep particles away from the filling/closing area.
- Ultraviolet air locks and door barriers must be used to separate areas of unequal risk.
- The air pressure of the changing room should be negative with regards to the manufacturing area corridor, but positive relative to external adjacent areas.
- Possible ventilation dampers, filters, and other services are designed and positioned in such a way that they are accessible from outside the manufacturing areas for maintenance purposes.
- All rooms and surfaces should be maintained and monitored for viable and non-viable particulates and the facility must be recertified on a semi-annual basis.
- HEPA-filtered air should be blown evenly to the entire clean room. The airflow must be uniform in velocity and direction throughout any given cross-section of the area.
- The air velocity should be 100 ± 20 ft/min.
- The vertical flow from ceiling-mounted HEPA filter units is utilized to protect critical sections of processing lines as well as workbenches.