For any sensor tech there is an equivalent stealth technology. Preysight Masks (Dark Heresy) is essentially a microfine set of cooling lines which reduce or eliminate your thermal signature. Sealed suits (at Mechanicum level of technology) would eliminate any odour/chemical trace. For that matter, refractory coatings can make armour functionally undetectable by specific wavelengths - see Legion where Alpharius calmly walks through a field covered in motion sensor 'tripwire' beams and doesn't set off any of them, despite making no effort to avoid them.
Haywire charges blow out sensors before they can trigger whatever alarm they may be connected to, or blind charges create a temporary...well...blind spot. Both might trigger an alert, but it depends on how smart the sensor is (not necessarily the Machine Spirit behind it, either - no matter how smart you are, if the alarm didn't go off, it didn't go off).
Picking out the bio-traces of an individual becomes night impossible if they are buried in an appropriate mass of bio-matter (hence why the damn things are of limited use in a jungle or on a tyranid ship) - not relevant here, of course.
Also, why on earth discount Psychic powers and sorcery? If in doubt, cheat laws of physics.
Imagine this set-up: A Heretek has set up a secret lab. It is currently empty, save for the automated defenses (he's a heretek, AI limitations don't apply to him). Any alert of any kind would either A. initiate a lockdown or B. void the research the PCs have come to get. How do you handle that, even assuming you have full details of the security measures (blueprints, traps, cameras, wavelengths recorded, etc...)?
Thanks for the answers!
Use correct access code, walk in, help self to recaff, pick up research, scribble insulting note on piece of flensed minion skin, leave.
The way to beat an impenetrable fortress is not to penetrate it, it's to get someone to let you in.
Ultimately, however convoluted the security protocols, there must be a way to disable them and get in or out, or he wouldn't have bothered building the place in the first place.
Thought #1 - extract appropriate access procedures from enemy minion
Thought #2 - make him think you've got hold of the access procedures, convince him you can and will make a play for the vault contents, then when he either goes to reinforce the defences or move the research, you have a window to get in where the self-destruct must be disabled.
Thought #3 - find something to offer that he wants more than the research. "Continued Existance" is usually a good starting point.
Edited by Magnus Grendel, 04 September 2013 - 03:29 AM.