44 RACA Journal I January 2026
LABORATORIES technical
• Installation: The new filter, pre-sealed within its change-out bag, is carefully guided into the housing. The bag is cinched, repositioned and secured to create the next sealed stub for future maintenance.
• Verification: Once installed, the access door is resealed and the housing undergoes integrity testing before airflow is restored.
This process, though highly controlled, underscores why only trained technicians should attempt filter replacement. As Mngadi cautioned:“ The BIBO system is fail-proof in design, but only if procedures are followed to the letter.”
SEAL INTEGRITY: GASKET VS GEL A point of discussion during a Q & A segment concerned the different sealing mechanisms used in filter housings. Some units use gasket seals, while others rely on gel seals that form an airtight barrier when compressed against a knife-edge inside the housing. Although the two designs differ in method, both aim to maintain airtight containment. Importantly, if a gel seal is damaged, the filter must be replaced entirely to preserve integrity – there is no approved repair method.
TESTING FOR SAFETY No filtration system is considered operational until it has passed a rigorous battery of tests. Among the most common are:
• Pressure decay testing: Measuring whether the housing maintains pressure without leaks
• Filter integrity testing( DOP testing): Confirming that HEPA or ULPA filters capture 99.99 % of particles
• Leak testing: Using smoke or aerosol particles to identify breaches
• Visual inspections: Checking seals, gaskets and housings for signs of wear
Each test, carried out by qualified technicians, ensures compliance with international containment standards. Pressure decay testing, for example, involves sealing the housing, applying calibrated pressure and monitoring for any drop over time – with strict limits set by standards such as ANSI N510( standard provides requirements for field testing of nuclear power plant air cleaning systems).
The conversation then turned to how HEPA filter housings fit into a full laboratory HVAC layout, using case studies from BSL-3 laboratories in Angola and Burundi. These schematics, explained by Mngadi, highlighted the airflow design principles underpinning pathogen containment.
BSL-3 facilities are designed as‘ dirty spaces’ under strict negative pressure. Supply air, delivered via ducted systems, flows in a controlled path from clean areas through anterooms into laboratory hot zones, ensuring that airborne pathogens cannot escape. Exhaust air is never recirculated back into the system, although energy recovery through heat exchangers is sometimes applied.
All potentially contaminated air is extracted via exhaust ducts, directed through biosafety cabinets( BSCs) and then channelled into BIBO housings. Although biosafety cabinets themselves are fitted with HEPA filters, Mngadi stressed that relying on them alone introduces risk:“ If a filter inside a cabinet develops a tear or loses seal integrity, pathogens could bypass containment. The BIBO housing provides a secondary protective barrier – a second chance to capture those particles before they escape.” RACA
Continued in part two in February …
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44 RACA Journal I January 2026
AIR CONDITIONING