General objectives of the stage: Decontamination is the second and at the same time the shortest stage of Death Factory mission. Your main objective is accessing the door leading to silo and as you've probably guessed, it is very well guarded.
Follow characters visible in front of you. Move past the room where one of the guards walks in - there is nothing interesting inside except more hostile characters. Stop after reaching the main area of explored location - a locker room.
In the locker room you can encounter both factory guards and scientists, so you have to watch out not to be exposed. During the exploration of the area ignore the right door, because it leads to the canteen, where a party takes place (this area is connected with one of challenges). It is worth noting that near one of closets you can find ready-to-wear scientist disguise (screen above) and it can be helpful while obtaining a secret described later.
If, for a change, you would like to obtain factory guard disguise, the safest way to do it is to enter the shower room located on the left. Find a valve shown on the above screen and turn it thus "encouraging" one of guards to check the problem. Use the advantage of very limited range of view of your enemies and kill or stun the guard, getting rid of his body in a nearby chute.
Before leaving the decontamination you have to disable one more security system and in order to do this you have to get into the right room, with several guards watching TV. Regardless of the difficulty level I recommend using the shutter to get inside, thus avoiding the guard watching the entrance.
A computer terminal you're looking for is shown on the above screen - during hacking you won't be luckily exposed by characters gathered here. But this simplification doesn't apply to evidence lying on the table. In order to safely collect this secret it would be best to use scientist disguise or (after stunning one of persons wearing blue clothes) researcher disguise.
If you play on lower difficulty levels then you can reach silo with the main passage shown on the above screen. But in this situation you have to wear factory guard disguise (scientist disguise is not enough) and use Instinct so none of guards can expose you.
A safest way to get to your target is a ventilation shaft. Its entrance is located in the toilet adjacent to the room with guards watching TV (screen above). After exiting the shaft turn left. Regardless of your actions, you need to access the door leading to the silo (R&D).