We do have O2 in our office, but I think it is a leftover from when we had a child with serious respiratory issues.
I am starting my third year at this school and haven't had to even look at it (THANK GOD)! I plan to check it out tomorrow.
I do use it to tease teachers and principals with. We have an autistic child who is a runner. Whenever he takes off, I usually wheel the O2 out "just in case." They don't always appreciate my humor, but I do!