If your problem is claustraphobia, which is fear of enclosed spaces then you need to do a few things to work through this.. Phobias are a fear reaction and that means your mid-brain takes over and drives up your heart rate/ respirations and begins to reduce the effectiveness of your senses and motor skills. The keys to overcoming phobias is to develop breathing skills to calm yourself down and follow a disciplined progression of drills to develop "cell memory" that will make wearing the mask and SCBA more tolerable.
1. Perform a "search" of fire engineering's web site for the Reilly emergency breathing technique, practice this method of breathing without a mask possibly while walking on a treadmill . This is a technique that can help offset the phobic reaction when it begins; you need to recognize the onset of the problem to begin to control it. Breathing will help regulate the increased heart rate/ respirations and reduce the phobic response.
2. Progress to doing the R.E.B.T. with only a mask on and when comfortable add the SCBA and gear, keep repeating the drill until you are more comfortable.Allow time to develop your comfort possibly up to 3 times a week for a month. If you don't have a treadmill we used to do a series of three drills when I started out, we started out by first sitting down in a chair and breathed the bottle down to see how long it would last. We then would do dtation duties on air (light work) to see how long the bottle would last and finally for the nut cases like me we performed hard work a circuit of burpees/ pull ups/ push-ups/ step ups until we exhausted the bottle.
3. Now it is time to move into more challenging training, we combine work in a tower with smoke to perform emergency rescue operations with the goal of challenging the Ff's fine motor skills. An example would be to take an SCBA apart and search for the parts and assemble with gloves on or if you have a partner do a mask and bottle change (search Fire Engineering). With these drills activate and silence the PASS device, use a radio to send a May Day etc. If a tower or smoke are not options put your balaclava on backwards to reduce vision and set a couple of rooms up with obstacles to do your search in. We also have constructed a confined space SCBA maze to teach air management, profile reduction, breaching walls etc to further enhance skills.