On the part where you have to get past the infared sensors and if you touch..

There are several control units that you must shoot to deactivate the IR sensors. I believe that there are a total of three. They are small boxes with a bright green light on them. To deactivate them, you must shoot them with a gun firing normal ammunition, i.e. the USP, because the tranquilizer gun will not work. When all of the control units are disabled, you will be able to hear the IR sensors shut down, you can check to make sure they are diabled with the thermal goggles or the cigarettes. Hope this helps.

There are a lot of infared sensors!! you have to make sure you shoot all the green blinking lights!

They're a total of 10 sensors you have to shoot. Above the door behind you, the two by the stairs, the one directly in front of you, one on the far left side on the deck, the two on both sides of the far door, one on the sentinal, one behind the flag, and one behind the group of birds on the left ledge.

The number of control units varies on each difficulty level. You'll need the sniper rifle to hit a lot of them. (Unless you're just an extremely good shot) The toughest one is on top of a cypher (uav, flying white circle thing). Make sure you hit the control unit, not the cypher. If you hit the cypher it will fall down and blow up the semtex. Mission failed! I would recommend using the socom on the three control units close to you so you don't waste sniper bullets. Hope I helped.