HEPA filters are one of the most reliable and dependent filters used in the pharmaceutical industry. They help mitigate problems related to contamination in the air to increases the efficacy ,quality and safety of the pharma process
What is a HEPA filter?
HEPA stands for High-Efficiency Particulate Air and is a mechanical filter designed to filter out much of particles, typically up to 99.7%. These includes pollen, dust, mold, bacteria, and common airborne particles of the size of 0.3 microns (µm).
They are the main components of filtration in a given pharma process and equipment, widely used in all critical pharma processes, specifically that required high degree of purity.
To use HEPA filters in any system and if large sized particles are present in the air, initially large-sized particulate filters are placed to remove large sized particles. When the air only contains small sized particles. After that, the air is exposed to the HEPA filter, to eliminate the remaining small particulates. This configuration increases the life and efficiency of the HEPA filters because directly exposing the HEPA filter to large particles will affect the physical structure of the HEPA filtering media.
In the pharmaceutical industry, HEPA filters air in critical areas, such as injectable filling and clean rooms.
Construction and Working
HEPA filters are mechanical filters made up of randomly arranged fibers of materials such as polypropylene, polyester, or fiberglass in a pleated form. The pleated structure creates a narrow pathway for the air to pass and traps oversized particles.
The HEPA filter’s working can be divided into any of the three mechanisms: diffusion, interception, and impaction.
Diffusion - This phenomenon occurs for the particles below 0.3µm, when the particles collide with gas molecules. The collision delays the passages of smaller-sized particles from the filter media, and ultimately collides with the filtering material. The delay and collision increase the probability of the other techniques (interception and impaction) to come into action and stop the particles.
Interception occurs when the particle flowing in the air comes in contact with the filtering material (fiber) and is captured to prevent flowing across the filter. The effectiveness of this phenomenon depends on the filtering material sizing, which increases when the material size is close to the size of the particle.
This phenomenon is effective for mid-sized particles.
Impaction - This phenomenon occurs for large-sized particles because they cannot avoid the material's fiber and end up being caught up by the HEPA filter.
Design considerations
Design considerations for HEPA filters are their attributes, which impacts their effectiveness in air filtering. They can include the following:
Air flow rate
It is the rate of air flowing across the filtering media in a given unit of time. It is critical because HEPA filters consist of dense material that can obstruct airflow. The selected HEPA filter must provide a specified airflow tailored to a specific process or application, which must be considered during equipment or process design. This is important because some pharma process or equipment requires specific airflow for their process to occur. Installing HEPA filter reduces the existing airflow, which is consider when designing a process, and it depends on the design of HEPA. If the airflow of HEPA filter fluctuates from the its design flow, it will also affects the process airflow, which is not good
Additionally, as the filter becomes clogged with particles, the air pressure reduces, and the resultant airflow is less than the design flow. The HEPA filters must be regularly maintained and replaced if required to prevent this condition.
Particulate Size
Particulate size is the parameter that defines the ability of a HEPA filter to filter out the flowing air through it. Indicated in the percentage, it represents a specific particle size.
The particle size can be 0.1µm, 0.2µm, and 0.3µm, and the efficiency can be 99.97& 95%. Higher efficiencies and smaller particle sizes can also ...
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