Choosing filter media: Why are glass fibers often preferred as a filter medium in bioprocess air/gas filtration?

Introduction / Context:
Filter medium selection influences energy consumption, safety, and reliability in sterile air handling. Glass fiber media are widely used in HEPA-grade and process vent filters because they combine high efficiency with practical pressure drops and robust thermal/chemical resistance.

Given Data / Assumptions:

• Dry or mildly humid air/gas streams typical of fermenter inlets or exhausts.
• Compatibility with common sanitization procedures.
• Need for low resistance to flow at specified face velocities.

Concept / Approach:
Glass fibers create a random mat with high porosity and fine diameters, delivering low pressure drop for a given efficiency. They resist wetting (compared with some organic fibers), maintain structure at elevated temperatures, and are non-combustible, which improves fire safety and durability.

Step-by-Step Solution:
Compare media: glass vs. cellulose/polymer fibers.Assess pressure drop at target efficiency; glass mats show favorable ΔP.Check resilience: glass fibers resist wetting, heat, and combustion better than many organics.Conclude that the combination of low ΔP and resistance makes glass fibers favorable.

Verification / Alternative check:
Manufacturer data sheets report low initial resistance and high temperature ratings for glass fiber HEPA media, aligning with bioprocess requirements for steam/heat exposure near equipment.

Why Other Options Are Wrong:
Higher pressure drop options raise blower power and operating costs.

“More liable to wetting or combustion” contradicts the known advantages of glass fiber media.

Common Pitfalls:

• Exposing glass fiber media to liquid water slugs; although resistant, performance can degrade if flooded.
• Assuming all glass media are identical; binder and fiber diameter distributions vary by supplier.

Final Answer:
They produce a lower pressure drop and are less liable to wetting or combustion