My ears block up while she is taking me down to the deeper depth - but no problem - it is just like when you are on an airplane - I just swallow and my ears open up - plus she allows you to take in a "sippy cúp" with water to drink while in there if you need to for your ears.
But I really don't have such a problem....
Funny, you smelled oxygen and I never have - I should ask her tomorrow when I go why there is no scent of oxygen.