According to the RCW this was called the "Protective Collector room". Most of the equipment is gone, but there would have been at least one and possibly two large air filters here. Air would come in from the outside, go through the filters then into the GPMTCP side of the building, the GCP wasn't set up for filtered air. Filtered air could also be piped to the airlock to use to decontaminate personnel entering the building during a gas attack. Based on what's in the other gas protected facilities there would have been a bypass on the filters so that air could be brought straight in from outside to the provide fresh air without using the filters unnecessarily.

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