Difference between positive and negative pressure containment systems
Isolators are an arrangement of physical barriers that use containment as a strategy to create an enclosed working space detached from the surrounding environment. Isolators enable manipulation of the processes within the enclosed space from the outside without compromising integrity.
Isolators have to perform two functions. They are a key control measure in protecting operators and the environment from exposure to potent molecules, many of which can be hazardous to health, and also in other cases protect the product from microbiological contamination and related factors during material handling and operations.
Isolators use a variety of methods to ensure the integrity of the clean environment, including positive and negative pressure systems that are maintained through closed-loop control of the chamber pressure. In this post, we highlight the differences between positive and negative pressure systems and their use in the pharmaceutical and biotech industries.
The first significant point of difference between the two is that positive pressure containment systems protect the process while negative protects the person.
Positive pressure essentially means that the pressure inside the containment system is greater than the pressure outside it. To illustrate, when you deflate a balloon, air rushes out because the air pressure in the balloon is higher than the pressure of the ambient air. Positive pressure is achieved by running exhaust air at 10 – 15 per cent lower than supply air.
Positive pressure containment systems are used in industries where the integrity of the process must be kept sacrosanct. In the pharmaceutical industry, positive pressure containment systems are used in sterile processes when protecting the process is of particular importance and the priority is keeping any possible germs or contaminants out of the Isolator. In the event of a leak, clean air is forced out of the isolator, rather than contaminants being allowed in.
Isolators are fitted out with gas board systems to remove oxygen (O2), and moisture (H2O) from helium, argon, nitrogen, or whichever combination is called for to create an ideal inert (chemically inactive) atmosphere. For example, when working with flammable products that react readily to oxygen.
Isolators for aseptic applications have a positive pressure of at least +60 Pa that serves not only as a physical barrier, but also a dynamic pressure barrier to protect the Isolator Class A (ISO 5) from particulates.
Negative pressure containment systems are used to protect the operator and the environment from unsafe material including a wide range of potent or hazardous molecules, active ingredients and volatile drugs. In hospitals, they are also used to quarantine seriously contagious patients.
Negative air pressure systems are the perfect choice to minimise airborne toxins from escaping the isolator and entering the cleanroom environment. Windows are sealed, and as a result of the lower pressure, air flows into the isolator rather than outside it. To illustrate, when you push an empty bottle into a bucket of water right side up, water flows into the bottle because it has lower pressure than the water surrounding it.
Negative air pressure is maintained in the work area, relative to the interchange compartment. Negative pressure containment systems are of two types – Recirculating Air or Total Exhaust.
In a negative air pressure containment systems, the air pressure in the Isolator is lower than the pressure outside it. This is achieved by running the inlet air at 10-30 per cent lower than the supply air.
Negative pressure is maintained from -30 to -20 Pa, to prevent particles from escaping the isolator. This serves as the physical barrier, but also a dynamic pressure barrier to protect the cleanroom Class A (ISO 5) from escaping particulates.
Negative pressure containment systems can be equipped with just about any type of pharmaceutical process that is needed.
Fabtech’s Containment systems can be used for tablet and capsule manufacturing, injectables, APIs and customised solutions from laboratory to production scale. Use the form below to request more information about our Containment Systems.