[pizza234]

Happened to me once. I was emptying one of my child’s thermoses in the bathroom when it suddenly "exploded" and sprayed the contents all over the bathroom walls. Quite a remarkable day :)

I didn't consider it a defect, though. I can hardly imagine cheap products adopting this solution.

[ludicrousdispla]

I would have thought they could design the screwtop so that it would relase pressure before fully disengaging the lid from the flask.

[teruakohatu]

That is what I was wondering. I would have thought it would need to be opened at eye level for the contents to hit the eye before being depressurised.

[altacc]

If it's a forceful opening and you're not holding the top tightly, then I imagine the top could launch upwards. I know from experience this can also happen if you put just a bit of boiling water in and seal it. The air expands under heat and will push the top out whilst you're unscrewing. A version of this top comes with a metal spoon & raised holder built in, providing some edges to hit you with and an extra projectile.

[jofzar]

Nah I think most people would open it at waist level standing with the lid facing up (towards you face as you are looking down), and twisting to open.

I can totally see how that would fly straight up at your face.