Suzie Dudas’s two children, nine-year-old Zale and Saxon, 7, were were in a family friend’s swimming pool when they used scuba tanks unknowingly filled with helium instead of oxygen.

A helium leak in a Falcon 9 launch can be particularly problematic due to the rocket's reliance on inert gas to pressurize its fuel systems. Falcon 9 uses supercooled liquid oxygen (LOX ...