The third one is on the floor and is pressure-sensitive. The slightest increase in weight...

Ethan Hunt: [Narrating, as William Donloe enters the vault] The terminal is in a black vault lockdown. The only person allowed in the room has to pass through a series of security checks.\nCIA Analyst William Donloe: [to keypad microphone] William Donloe.\nEthan Hunt: The first is a voice print identification and a six-digit access code.\n[Donloe types in a code and enters the outer room]\nEthan Hunt: This only gets him into the outer room. Next he has to pass a retinal scan.\n[Donloe passes the retinal scan]\nEthan Hunt: And finally, the security measures are only deactivated by a double electronic keycard... which we won't have.\n[Donloe scans his card, enters the vault, and logs in at the terminal]\nEthan Hunt: Now, inside the black vault, there are three systems operating whenever the technician is out of the room. The first is sound-sensitive. Anything above a whisper sets it off. The second system detects any increase in temperature. Even the body heat of an unauthorized person in the room will trigger it if the temperature rises just a single degree. Now, that temperature is controlled by the air conditioning coming in through an overhead duct, 30 feet above the floor. That vent is guarded by a laser net.\n[Donloe leaves the vault, security measures activate]\nEthan Hunt: The third one is on the floor and is pressure-sensitive. The slightest increase in weight will trigger the alarm. And any one of these systems, if set off, will activate an automatic lockdown. Now, believe me when I tell you, gentlemen, all three systems are state-of-the-art.\n[condensation from Donloe's drink drops to the floor sets off the alarm]