There are two doors you can open with the lockpick you obtain from the start, you have to pick one. One room has a lvl 1 keycard, the other has a lvl 2 keycard (if I remember correctly). Each room is ideal for a specific goal. One is necessary to cleanse squidrabbit infection, the other is ideal if you don't have squidrabbit and plan to do other things. There is a lvl 3 card which can be obtained inside the lab, but there is no lvl 4 actually inside the lab proper.