Since you'll be practicing pocket mask use during your PADI Rescue Scuba Diver course, youll want to disinfect your pocket mask before transferring it from one person to the next. 

The easiest way to do this is to do this soak the mask for at least a minute in a sanitizing solution of 50 milliliters / 1/4 cup house bleach to 4.5 liters / 1 gallon of water. Rinse the mask thoroughly in fresh water and shake dry. Dry any excess with a clean towel. 

You can also use this on other plastic rescue equipment, including the no vented masks used on no resuscitator demand oxygen systems. Dont attempt to sanitize any other oxygen system component except masks, however.