I use to travel in lift.but 3 to 4 times i got stuck in it where it was full dark and it mad me feel so low in oxygen.its been years i use to travel in lift.but those incidences made me stop using it.i started feeling low in oxygen in closed areas where there is AC and no window open.i know there is no such place where there is less of oxygen.even in flights i started to feel low.i was staying at 15 th floor and no window open.full AC .those 3 days where night mare.i use to run out of hotel to just breath where 1000 of people are there in that hotel.