Headscratchers / Star Trek Deep Space Nine S 03 E 07 Civil Defense

• This episode notes that the Federation removed the "deadly force-field" widgets when they took over the station. So then why did they miss/ignore the "flood any room with lethal nerve gas" feature on the life support system?
  • The force-field widgets were probably easier to find.
  • The life support system likely functioned on the premise of replication, meaning that the air was replicated. It's also likely that Dukat's program overrode the replication portion of the life support system to generate such lethal gas to kill the crew.
• In all the time Starfleet had control of the station they never had the time to do a through search through the computer for such programs? And if so entrenched replace computer cores with Federation computer cores?