Yes. Most CPAP machines and facemasks will fit inside your carry-on luggage. However, since CPAP machines are considered necessary medical equipment, they may travel in their own case without being considered an additional carry-on item. You may want to get a letter from your doctor explaining what your CPAP machine is and why you need to travel with it, although they’re common. Most security personnel should be familiar with them. Because sleep apnea doesn’t ever take a vacation, you shouldn’t either without taking your sleep apnea treatment with you when you travel.