ST. PETERSBURG — A witness getting his morning newspaper told police he saw a bright flash when a scuba tank exploded early Sunday morning.
The man holding the tank, avid diver Russell Vanhorn II, suffered what appeared to be burns in the blast that took his life and destroyed the condo he was standing in, according to St. Petersburg police.
As investigators continued their search Monday for answers in the puzzling blast, those potential clues suggest pure oxygen could have played a role in the explosion that killed the 23-year-old Iraq war veteran.
"That signifies to me that oxygen was involved and not just compressed air," said Doug Jackson, vice president of Bill Jackson's Shop For Adventure and a certified diving instructor and trainer. Jackson said pure oxygen increases the risk of fire and explosion.
Most recreational divers use compressed air — the same mix of 78 percent nitrogen and 21 percent oxygen we all breathe on land — in their pressurized cylinders. But pure oxygen is used for much more advanced and riskier diving, such as cave or deep diving.
Pure oxygen can be used for decompression, for example, to help divers purge themselves of nitrogen before surfacing from deep depths. That's to prevent decompression sickness: gas bubbles that can develop in the body and cause pain, paralysis and even death.
If pure oxygen was being used for a diving trip in the Tampa Bay area, Jackson said, that suggests Vanhorn may have planned to go cave diving.
Because of its explosion risk, pure oxygen should only be handled by skilled divers using special procedures and the utmost care, Jackson said.
Exploding scuba tanks are rare and devastating events. But in cases such as the 1981 blast that cost a Lakeland man his legs, the cause of the explosions appeared to be catastrophic failure of the pressurized metal tanks — not the gases inside the tanks.
Russell Vanhorn Sr. said his son enjoyed cave diving as well as other forms of diving in both Florida and his native Iowa. But his son was always careful.
"He enjoyed deep diving, he enjoyed open diving," said Vanhorn Sr., 55. "I know he did some cave diving, but he didn't do it on a regular basis.
"He would take pictures of underwater volcanoes down there. He said, 'Dad, I don't do it all the time. I do it with a bunch of guys and we're always safe.' "
The complicated nature of the investigation led St. Petersburg police to take over from the Fire Department.
Police spokesman Mike Puetz said investigators will track down the history of the exploded tank, determine who inspected and serviced it in the past, who recently filled it and with what kind of gases.
The tank was found split down the middle from top to bottom, lodged overhead in what was left of the kitchen ceiling. The blast shattered drywall and ceiling, collapsed walls, smashed furniture, blew out the doors and windows and damaged cars in the parking lot.
The Tampa Bay Regional Bomb Squad came in to inspect and empty the 11 other tanks found inside. Authorities did not say what was in the tanks.
Sara Swoch, 27, and Brent Stevens, 22, were inside the condo at 5865 37th Ave. N when the tank exploded at about 6:50 a.m., police said.
Swoch lives in the condo. She and Stevens were in different rooms when the tank blew up, police said, shielding them from serious injury.
Master scuba diver trainer Joyce Hannaseck of Narcosis Dive Shop in Tarpon Springs went diving with Russell Vanhorn II over the summer. She said the Tampa Bay diving community is anxious for answers.
"We're all just holding our breath to find out what caused this," she said.
Times researcher Carolyn Edds contributed to this report. Jamal Thalji can be reached at firstname.lastname@example.org or (727) 893-8472.