The Proper Way to Use an Oxygen Mask in the Event of a Midair Emergency

After a Southwest Airlines emergency Tuesday, many noticed that some passengers were not wearing their oxygen masks properly.

When a Southwest Airlines flight descended to Philadelphia International Airport in an emergency descent following an engine explosion, Marty Martinez thought he was going to die. 

"I remember in that moment thinking, 'This is it,'" he told Inside Edition. "I thought those were my last few moments on earth."

Martinez took out his cellphone to record a farewell message for his family. In the chaos, he bought the $8 on-board WiFi so he could stream it on Facebook.

"I cared about being able to communicate and tell my family and friends back home that I loved them," he said.

With his oxygen mask in place, he typed messages. "We are bracing for landing!!!" he wrote.

But when the oxygen masks dropped, several passengers seen in photos and video taken by Martinez covered only their mouths and not their noses.

"This is totally wrong," said Dante Harris, the president of the Association of Flight Attendants. 

Experts say the masks are meant to prevent hypoxia, or lack of oxygen, at altitudes where the air is dangerously thin. Only covering your mouth increases the chance of hypoxia.

Experts say it is also important to pull the straps tight against your face. 

The oxygen lasts for around 12 minutes to allow the pilot time to reach the breathable altitudes at 10,000 feet, as newly minted hero Tammie Jo Shults was able to do, saving more than 170 lives.

"This is critical information that could one day save your life," Harris said.

Martinez credits Shults for her composure.

"To think I have a second chance on life," he said. "I feel completely in debt to her."

He was sitting just two rows away from Jennifer Riordan, who was killed after she was partially sucked out of the broken window.

Martinez said the airline allows people to pick their own seats.

"To think that could've been any one of us... My heart goes out to that woman and her family," he said.