NEW YORK CITY (PIX11) — Only 16 people survived the collapse of the north tower on 9/11.

Among them was Port Authority K-9 unit officer Dave Lim, who shared his story with PIX11 nearly 20 years after the terrorist attack.

Lying in dust that day after the towers fell, Lim didn’t immediately understand his own fate.

“The strangest thought came to my mind … ‘dead men don’t cough, so I must still be alive,’” Lim said.

Lim began his shift on Sept. 11, 2001, like any other, but when the first plane hit he ran to help.

While directing people to stairwells, Lim said he encountered a woman named Josephine Harris.

At the time, Harris was exhausted and unable to walk, so Lim said he stayed with her.

The north tower then came down on top of them.

“It was more like an avalanche or the sound of an on-rushing locomotive. You can feel the air as the floors are pressing down on each other,” Lim remembered. “It felt like a hurricane.”

When it all stopped, 110 stories of the World Trade Center were on top of Lim and Harris. They were among the 16 people who survived the north tower collapse by being inside a pocket on the fifth floor of stairwell B, and the only way out was to go up.

“That’s where we saw what was a light, and I thought it was the light on the sixth floor. It turned out to be the the sun,” Lim said.

Reflecting after nearly two decades, Lim said people often say he must be blessed or have a greater purpose.

“I have a hard time accepting that fact. It’s not that i don’t believe in God or that God did not save me. It’s just that I don’t feel I’m as deserving, or any more deserving, than those 3,000 people that were killed,” Lim said.

That day did change Lim’s appreciation for life, though.

“I’ve learned to appreciate the little things in life, like my daughter’s concert or just sitting on a bench and enjoying nature, things I never had time for.”