Two college students were found dead inside a large, deflated helium balloon after apparently pulling it down and crawling inside it, officials said.

The deaths of Jason Ackerman and Sara Rydman, both 21, appear to be accidental, Hillsborough County Sheriff's Maj. Bob Schrader said.

Their bodies were found Saturday partially inside a deflated helium balloon at the entrance of a condominium complex a few miles north of Tampa. The 8-foot-diameter balloon was used to advertise the complex.

"It was more a fun thing they thought they were doing," said Linda Rydman, whose daughter was found dead. "You know how you blow up the balloon and suck the helium."

The county medical examiner said Sunday that the cause of death won't be released for six weeks, until toxicology results come back.

Inhaling helium can quickly lead to brain damage and death from lack of oxygen, according to the Compressed Gas Association, which develops safety standards in the gas industry.


Helium Precautions

The voice of a person who has inhaled helium temporarily sounds high-pitched, resembling those of the cartoon characters Alvin and the Chipmunks or pinky and Perky (although these characters' voices were produced by shifting the pitch of normal voices). This is because the speed of sound in helium is nearly three times that in air. As a result, when helium is inhaled there is a corresponding increase in the resonant frequencies of the vocal tract. The higher perceived pitch is only due to a different frequency shaping of the voice, the fundamental frequency of the vocal cords remains more or less the same.

Although the vocal effect of inhaling helium may be amusing, it can be dangerous if done to excess. The reason is not due to toxicity or any property of helium but simply due to it displacing oxygen needed for normal respiration. One must be aware that in mammals (with the notable exception of seals) the breathing reflex is not triggered by insufficient oxygen but rather excess of carbon dioxide. Unconsciousness, brain damage and even asphyxiation followed by death may result in extreme cases. Also, if helium is inhaled directly from pressurized cylinders the high flow rate can fatally rupture lung tissue.