Breathing in helium “deprives the body of oxygen, as if you were holding your breath” but in general, deaths from helium are extremely rare, specialists say. Mylar Balloons also known as Foil Balloons – number 3 as this balloon type was – can have up to 12 oz. / 15 cu. ft. helium inside. They are special balloons which resembles a slightly flattened sphere.Pat McGloghlon, the girl’s grandmother, says she wants to spread the story to warn parents about the dangers of balloons in their home. The craze of inhaling helium is a party trick spreading across the U.S, with users getting a comical high-pitched voice after inhalation but deadly accidents occur.