I have a question for you PSD whom have delt with this type of situation..... I will soon be finishing my DAN Diving Emergency Specialist (DES) rating,,,,which among many preq. courses you must have DAN O2 and DAN Adv. O2 plus AED certf. just to mention a few. **My question is when you have been adm. CPR and O2 via an oronasal mask to a patient and then an AED unit comes available,,,,,,do you need to remove the mask/O2 from the patient to adm. the AED shock to avoid explosion-fire,,,,,or is this not a threat? I feel I know the answer,,,,that being it poses no great danger,,in that it is done in ERs daily,,,,but I still want to cover myself just in case the "perfect world" setting with all the tools ever happens.