OKLAHOMA CITY -- If an EF-5 tornado is bearing down on your house, where would you want to be? In an above ground safe room, or below ground shelter?
It depends on who you ask.
"Like the weather people always say, when you're facing an EF-5, the only way to survive the thing is to be below ground," Kris Pettigrew, owner of Precision Shelters said.
"(That's) old school," Mark Webb, owner of Armor Vault responded. "People just grew up with people going underground. Technology has developed."
It really has. Videos of safe rooms and shelters getting tested at Texas Tech's National Wind Institute shows that change.
They have to withstand a 15 pound 2x4 being projected at 100 miles per hour.
Webb's Armor Vault above ground safe rooms passed that test.
"I don't care where you put this," he said. "What hits it is not coming through."
Pettigrew said it's safer to be underground because tornadoes throw around much heavier items than 2x4's.
"You take that abnormal circumstance where an actual car actually gets thrown directly at it, then I'd question it (the safety)."
But what about the issue of being stuck inside after the storm?
The underground shelter door slides open.
"So you can still open the door and try to at least force your way out," Pettigrew said.
But Webb says above ground safe room doors are safer, because they open inward - so you could crawl out over debris.
"It's virtually impossible to get trapped inside the thing," he said. "You're not going to get trapped inside this unit."
He also says above ground safe rooms are easier to get into for seniors and those with physical disabilities.
Virginia Peters takes all of ten seconds to go from her house to her safe room in her garage.
"The older you get, it's harder to get down into underground kinds of things too," she said.
Elaine Furr was pelted with hail as she ran across the street to her neighbor's outdoor concrete shelter in Moore, May 20th.
"The noise and the roar and everything. I just felt like it was just going to pull that door open, even with it locked like that," she said.
Although she was exposed to the elements before taking shelter, she said the risk was worth it to get underground.
"I love (that shelter)," she said, "because it saved my life."
John Bourdeau is with FEMA, and was part of a team that analyzed how aboveground and below ground shelters held up during May 20th.
"We found that nearly everything performed well," he said.
In fact, he has never seen either shelter fail anywhere around the country that met FEMA's P-320 specification guidelines.
"If they say they're FEMA compliant, you want to get an independent source to double check on that," Bourdeau said.
FEMA did find one garage floor shelter that filled completely with water after everyone got out.
To avoid that, Bourdeau recommends doing what Precision Shelters does.
They elevate the concrete slightly up to the shelter from the garage floor so that it diverts water around it.
For concrete shelters, make sure they're waterproof.
Whatever you choose, he says ask for numerous references of satisfied customers.
"I would like to see as many people on that referral list," Bourdeau said. "Addresses and phone numbers. 15 would be good. More is better. I would call five. Tell me how it went?"
Don't forget to register your shelter with your city so they'll know to look for you immediately after a tornado hits.
Get an independent source to verify that a shelter is FEMA compliant.
For a list of companies that have passed the Texas Tech impact test, click on http://www.Depts.Ttu.Edu/nwi/research/debrisimpact/downloads/shelter_above_ground_%20oct2013.pdf