While helium was flushed through the document enclosure, periodic checks with the leak detector revealed the degree to which oxygen had been displaced with pure helium. After all of the air was replaced by helium, the inlet and outlet tubes were sealed and removed from the enclosure. E. C. Creitz (pictured) was connecting the ammeter to the conductivity cells during the flushing operation.
National Institute of Standards and Technology
National Institute of Standards and Technology