Gas Filter Housings

A gas filter housing is a pressure-rated vessel used to hold filter cartridges that remove particles, bacteria, or other contaminants from process gas streams. These housings combined with sterile gas filters ensure sterile and clean gas delivery in industries like pharmaceuticals, food and beverage, biotech, and electronics manufacturing. 

However there most important feature is that they are designed for low pressure drop which is essential in gas filtration to reduce running costs to a minimum. Also the design has a plenum chamber which the inlet gas flows into initially prior to filtration. This ensures that if there is any entrained condensate or other liquid in the gas stream it is diverted into the bottom of the housing. This prevents blinding of the gas filter preventing operational issues.

• Sterile Gas housings are designed for pressurised gas filtration using hydrophobic PTFE to remove microbes and particulates.
• Sterile Vent housings are non-pressurised filters allowing tanks and vessels to breathe while blocking microbial ingress during fill or emptying cycles, maintaining aseptic conditions within the tank or vessel.
• Heated Sterile Vent housings include external heating elements or jackets to prevent condensation on the cartridge filter, which could blind impairing airflow or compromise sterility—particularly important in cold environments or moist gas streams.

When selecting a gas filter housing, consider the following process:

• Size the cartridge filter system to know the number of 10” modules to be housed at the required Flow rate (Nm³/h) and desired clean pressure drop
• From the operating pressure of the system choose a housing with connection and inlet/outlet connection to support these conditions
• Understand the pressure or safety regulations that apply to the system and ensure the housing is designed to meet them.

Most gas filter housings are made from 316L stainless steel due to its corrosion resistance and hygienic properties. Other options include carbon steel or special alloys like Hastelloy for aggressive or high-temperature environments. Surfaces are often electropolished to reduce microbial retention and improve cleanability. Gasket and seal materials (e.g. EPDM, silicone, or Viton) must also be compatible with the process gas, but also be compatible for steam sterilisation (SIP) of the system prior to use.

Pressure ratings depend on the application. Standard sterile gas housings are typically rated for 6–10 bar, while compressed air or industrial gas housings can be rated up to 16–40 bar or more. Sterile vent housings often operate at atmospheric pressure but must handle vacuum or overpressure scenarios. Always verify maximum allowable working pressure (MAWP) and ensure compliance with PED or ASME VIII codes.

Yes, housings for sterile applications are designed for repeated steam-in-place (SIP) cycles at temperatures up to 121–150 °C for between 30 and 60 minutes each cycle. They are also suitable for autoclave sterilisation.

Read more in out blog: How CIP and SIP can Extend Cartridge Filter Lifespan

In moist or cold conditions, vapour can condense inside the housing or cartridge. Heated sterile vent housings include a thermal jacket (typically steam or electric) that keeps the housing above dew point, ensuring condensate doesn't form on sterile PTFE membranes. This is crucial for applications like tank venting or humid gas handling in low ambient temperatures.

Differential pressure (∆P) monitoring involves installing gauges before and after the filter to measure resistance across the cartridge. A rising ∆P indicates clogging and helps determine when a cartridge should be changed. Typically, a pressure drop above 0.5–1.0 bar in gas systems suggests cleaning or replacement is needed to maintain flow and lower running costs.

Frequency depends on usage and gas cleanliness. For sterile air, cartridges may last 6–12 months, especially in clean environments. Applications involving high particulate or oil vapour may require more frequent changes. Always monitor differential pressure, inspect cartridges regularly, and follow manufacturer guidelines.

Yes. Most sterile gas filter housings are compatible with compressed air, CO₂, N₂, and other inert gases. Ensure pressure rating, material compatibility, and filtration performance meet system requirements. For compressor discharge applications, always use pre-filters to remove oil and moisture before sterile filtration.

Install vent housings vertically on the highest point of tanks or autoclaves to allow sterile air exchange. Use a hydrophobic 0.02 µm PTFE cartridge to prevent microbial ingress. Ensure proper condensate drainage and avoid dead legs in the piping to maintain sterility.

Routine tasks include:

• Replacing or cleaning cartridges based on ∆P
• Inspecting seals, clamps, and housing integrity
• Checking heating jackets (if present)
• Cleaning internals during cartridge replacement Always document sterilisation cycles and inspection intervals for regulatory compliance.