Hi! I entered a room, where a person who has chickenpox stays, for about 30 seconds. Is that enough to get me infected?

Secretions? . Your mention of "entering the room" implies you were many feet away form the patient, which is somewhat lower risk. That said, chicken pox is extremely contagious! If you have not had disease, get the shot at your local prim care doctors office tomorrow. It will minimize your chance of full blown disease, with its associated scarring, secondary staph infections and encephalitis. Hope this helps.
Depends. We started giving the vaccine in the US in the mid 90's so you may have been vaccinated, reducing your risk. The "90"sec in a room with an active case is enough to expose you.This is one of the most contagious diseases that can be spread through airborne droplets (cough) and direct contact.