The Magnehelic gage is the industry standard to measure fan and blower pressures, filter resistance, air velocity, furnace draft, pressure drop across orifice plates, liquid levels with bubbler systems and pressures in fluid amplifier or fluidic systems.
Differential pressure is the pressure which differentiates between the pressure of the atmospheric of one area (process area) to other surrounding areas (corridors). it is measured in pascals, for this Magnehelic gauge is used.
Why pressure difference in pharmaceuticals is important?
To prevent cross-contamination, contaminated particles generated during the manufacturing process may enter the air and could contaminate other manufacturing products.
WHO guidelines on HVAC system:
According to WHO Guidelines, it must maintain a pressure differential of 10-15 pascals between the processing area and therefore the surrounding area. the processing area should be negative ( just in case of OSD ) to the corridor area to ensure airflow from the aseptic area to the non-aseptic area.
Importance of the airlock:
While keeping positive pressure in the corridor than the processing or manufacturing area. the positive airlock should be there to minimize direct airflow from process air to the non-process area, which helps control the direct contamination in the processing area.
Airflow direction in the non-sterile area:
Always keep negative pressure inside the controlled area (process area) as compared to the corridor area (positive pressure) to prevent cross-contamination.
Negative pressure means clean airflow from the corridor going in the process room and contaminated air in the process area flows out from risers. These types of air systems are suitable for oral solid dosage, steroids and chemotherapy products.
Airflow direction in a sterile area:
Cross-contamination of one product with other products is an important issue because bacterial contamination risk is higher, that’s the reason why positive pressure is a must inside the sterile area as compared to the corridor.
Recovery Test for HVAC:
It’s important to perform a recovery test regularly to check pressure differential in pharmaceuticals produced by the HVAC system. calibration of the Magnehelic gauge must be checked regularly.
Building construction:
to take care of the integrity of the unit, it must be a typical construction of the building, airtight doors, and window installation is required to stop loss of pressure through the gap. An alarm for a sign should be available for workers to understand any loss of atmospheric pressure.
Maintenance of Pressure Differential
The importance of pressure differential in pharmaceutical manufacturing and how it is maintained to prevent cross-contamination.
The pressure differential is the difference between atmospheric pressure between the production area and its surroundings. It is measured in Pascal using the Magnehelic pressure gauge.
ALSO READ: Airflow Balance in HVAC
According to WHO guidelines on the HVAC system, 10-15 pascals of differential pressure is maintained between manufacturing and surrounding areas. The aseptic area should always be more highly pressurized than the non-aseptic area and airflow should be always from the aseptic to the non-aseptic area. This pressure differential is maintained by the HVAC system. In the tablet production area, pressure differential helps to prevent cross-contamination.
Dust particles are generated in granulation and compression area; those can contaminate the other products being manufactured in adjacent areas. In sterile manufacturing pressure differential prevents entering the particles and microbes in sterile manufacturing rooms.It is necessary to maintain a positive pressure in the corridor than the tablet manufacturing areas to minimize the cross-contamination. But positive airlocks should be there before entering the corridor while maintaining the positive corridor than the manufacturing rooms.
These airlocks prevent the direct airflow from uncontrolled areas to controlled areas and help to minimize the entrance of contaminated air into the controlled area. In the sterile manufacturing area, the manufacturing room is maintained under positive pressure than the surrounding corridor because there are more chances of microbial contamination instead of cross-contamination.
It is important to carry out the pressure differential and recovery tests at the time of HVAC system validation. Pressure gauges should also be calibrated at the time of HVAC validation.
It is important to have good building construction and airtight windows and doors to maintain the required differential pressure. Pressure drop alarms are also used these days to indicate low pressure in critical areas. The pressure differential may cause difficulties to open the doors, particularly in facilities having multi-level differential pressure. Some facilities are using sliding doors to prevent this problem but it is difficult to make the sliding doors leakproof.
ALSO READ: SOP for Calibration of Magnehelic Gauge
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