Introduction to Negative Pressure Cleanrooms

Negative pressure cleanrooms are being applied more and more widely, mainly in hospital operating rooms and wards, pharmaceutical factories, biosafety laboratories, medical device production lines, etc. It should be noted that for different types and purposes of negative pressure cleanrooms, the process layout, production flow, and environmental requirements for the clean areas are all different. Under the premise of meeting the general requirements of cleanroom environment, for example, some need to conduct leak detection of the high-efficiency exhaust system; some need to test the content of settled bacteria in the clean room; and some need to pay special attention to the pressure difference.

1.1 Concepts of Positive and Negative Pressure in Cleanrooms

Positive and negative pressure in a cleanroom are relative to the atmospheric pressure (absolute positive and negative pressure). In simple terms, positive pressure means the pressure is higher than the atmospheric pressure, while negative pressure means the pressure is lower than the atmospheric pressure. It mainly involves the air flow direction and the control of supply, return, and exhaust air in the purification air conditioning system. If the only requirement is to ensure a clean working environment, a positive pressure cleanroom is generally used, which is the most common situation in cleanrooms, such as electronic factories, photovoltaic plants, etc. If it is necessary to ensure a clean working environment without causing pollution to the surrounding environment, a negative pressure cleanroom is required, such as vaccine inactivation production workshops, animal houses, etc. Of course, the specific situation can be relatively complex. Some factories have both positive and negative pressure, and whether to prioritize positive pressure or negative pressure needs to be configured according to the actual situation.

1.2 Characteristics of Negative Pressure Cleanrooms

The airflow direction required for negative pressure cleanrooms not only needs to protect the products from being disturbed by external polluted air, but also needs to ensure that the contaminants within the operation area do not leak to the outside.

The negative pressure area must form an orderly pressure gradient. Depending on the different protection levels of each room, the absolute value of negative pressure in rooms with higher toxicity of pollutants is higher, so that the pressure in each room is arranged in a stepped manner, to ensure that the pollutants present in these rooms will not spread to the clean corridor, nor to the outside atmosphere. This is of crucial importance for the production safety of the negative pressure cleanroom.

The installation of the wall panels and doors/windows in a negative pressure cleanroom is of great significance, as leakage of the enclosure structure poses the greatest threat to a negative pressure cleanroom. If there are visible holes, incomplete sealing during installation leads to leakage; if there are tiny gaps, leakage occurs due to inability to seal during installation. Both of these situations result in incomplete sealing of the enclosure structure, making it extremely difficult to achieve 100% no leakage.

Maintaining the pressure gradient in a negative pressure clean room is quite challenging. Factors such as opening and closing doors, personnel entering and exiting, and the operation of the equipment's own exhaust system can all interfere with the pressure difference.

As the professional negative pressure cleanroom manufacturer, Suzhou Pharma Machinery has done more done 500 turnkey cleanroom projects all around the world. For more information, please contact us: pharma@sz-pharma.com.

Suzhou Pharma Machinery Co.,Ltd.

2026/03/13

Tia