RACA Journal I February 2026 www. refrigerationandaircon. co. za 43
LABORATORIES
• Final disposal: once chemically decontaminated, spent filters are bagged and sealed for safe disposal. In South Africa and much of Africa, the preferred method is incineration, especially in TB laboratories where the risks of pathogen release are high
Baxter added a cautionary note:“ If a bagged filter is sent to landfill, someone could open it, exposing themselves and others. Incineration eliminates that risk entirely.”
NEGATIVE PRESSURE / PRESSURE CASCADES Maintaining pressure differentials is critical to containment. BSL-3 labs operate at negative pressure relative to surrounding spaces, with the most negative zones being those where hazardous work occurs. Pressure cascades are carefully designed so that air flows progressively inward – from specimen reception( positive) to anteroom( neutral or slightly negative) to hot zones( strongly negative). This ensures contaminants never migrate outward.
Door seals, brushes and sometimes filtered door grills further protect against uncontrolled airflow. As Mngadi noted:“ Air will always follow the path of highest to lowest pressure. Our job is to make sure that path keeps hazards inside the lab – and away from the environment.”
While the principle of decontaminating a BIBO housing is consistent across laboratories, the technology employed varies. Baxter demonstrated the Curis decontamination unit, a compact mobile system mounted in a trinity cart with an integrated tablet interface. The unit introduces aerosolised hydrogen peroxide into the housing and recirculates it through the system until sensors confirm neutralisation.
The process is largely automated: once room dimensions and filter sizes are entered, the system calculates the correct dwell time. Status lights provide clear visual cues:
Cassandra-Anne Baxter( ALPA sales general manager), being acknowledged by SAIRAC Cape Town Centre.
• Flashing red: evacuate immediately, dispersal beginning
• Solid red: hydrogen peroxide release underway
• Amber flashing: dwell time active, safe to enter only with full PPELight off: decontamination complete, system purged
This approach reduces operator error and ensures a repeatable, validated decontamination cycle.
DECON BOX VERSUS MOBILE SYSTEMS The traditional decon box design, built directly into the HVAC system, fumigates not only the BIBO housing but also connected components such as fans. This approach accounts for the possibility of filter loading or delayed detection of leaks.
“ These units complement my solution very well – they offer the added ability to decontaminate the fan, as well as Camfil CamContains, and can operate using either our system or formaldehyde. Decon boxes and mobile systems can be applied together depending on the containment requirements.”
Supplied by SAIRAC Cape Town Centre technical
Supplied by ALPA
RACA Journal I February 2026 www. refrigerationandaircon. co. za 43