General assumptions: Destroying Ashford's research is the last objective of twelfth game mission. The most problematic might be a safely evacuation from murder place of Dr. Ashford.
Go again to an interactive valve and turn it to "blind" your enemies again for 30 seconds and making your evacuation easier. Turn around and move to the bridge control panel shown on the above screen, which becomes active only after eliminating both scientists. Interact with the panel and wait for the bridge. If enemies are alerted because of Ashford's death, make sure to stay hidden behind any cover.
Walk over the bridge, reaching Dr. Ashford's room. Start with playing the recording.
Finally sabotage two fuse boxes and use the only available passage, thanks to which you'll leave the test facility.