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 After all of the air had been replaced by helium, the inlet and outlet tubes were sealed and removed from the enclosure.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