A collapsed lung, also known as a pneumothorax, occurs when air escapes out of a lung and becomes trapped inside the space between the chest and lung cavities. This can be caused by air blisters in the lungs that break open, sudden air pressure changes, or trauma to the chest or ribcage.
The IRS interpreted this provision as applying only to full-time students. In a 1993 technical advice memorandum, the IRS provided a safe-harbor definition of a full-time undergraduate student as one who is taking 12 credit hours and working no more than 20 hours per week.
CAMPUS DEFINITION OF FULL-TIME STUDENT STATUS. The university defines full-time study as 12 units, however, while undergraduate course units are counted at face value, graduate course units (those numbered in the 200 series) are weighted at 1.5 units per each course unit.