How long does a rapid decompression take to equalize with the outside pressure?

• A. More than 30 seconds
• B. Approximately 20-30 seconds
• C. Less than 10 seconds
• D. It does not equalize

Answer: (C)

When a rapid decompression occurs, a large pressure difference between the cabin and the outside air drives air out through the breach until the cabin pressure matches the outside pressure. Because the outside air at cruising altitude is so much lower, this exchange happens in seconds. In practice, the cabin pressure tends to equalize in less than ten seconds. This quick equalization explains the sudden rush of air you feel and why immediate safety actions—like donning oxygen and descending—are triggered. The other timeframes are too long for how rapidly the air moves to balance the pressures, and saying it never equalizes isn’t accurate because the pressures do reach balance.