Protective measures must be implemented when PCB containing paints, coatings, caulks and secondary contamination on walls and ceilings are removed. Extensive removal work is carried out in a containment or decontamination area. The containment zone must be maintained under negative air pressure by installing negative pressure units with activated carbon filters. These are basically the same precautions as during Asbestos removals.

The filtered exhaust from the negative pressure units is usually routed outside the containment area and vented through appropriate filters outside of the building. This can be very challenging or even impossible, particularly if PCB removal work has to be done in tunnels, underground installations or basements without windows or without reasonably close outdoor access.

So, we are very pleased that for the first time, negative pressure units, specifically designed and equipped with activated carbon filters, were successfully tested in a circulating air system within decontamination areas during a demanding PCB remediation project in an underground installation.

Using such a circulating air system offers many advantages, such as great flexibility and independence of fresh air supply, as well as safety and reliability as long as appropriate devices and enough redundancy to cope with breakdowns are provided.

The difficult management of activated carbon has to be considered, as a penetration of fully loaded activated carbon cannot easily be controlled. A saturated HEPA filter would close the airflow and lead to an alarming drop in pressure. PCBs could then pass the activated carbon unnoticed; a so-called “penetration”.

Therefore the negative pressure units have been specifically designed with a redundant double filter system, including two filter cartridges with activated carbon. The type of activated carbon must of course be appropriate for PCBs. Due to the upstream H14 filters the usage of the activated carbon is quite economic. Analytical testing after replacement of the activated carbon provides valuable information about the level of saturation and the best average time of replacement, which however may vary from site to site. Used activated carbon has to be disposed of according to the waste regulations for PCBs, and therefore by high temperature incineration. The filter cartridges can be decontaminated and used again.

Thanks to a monitoring station outside the containment area the negative pressure units can be programmed to automatically maintain the required negative pressure in the containment area.