Yes, they usually are encased with quite a few openings into the PC case. The air to cool the PSU comes more often than not from inside the PC. Even if the fan sucks air out of the PC, once the PSU starts to burn the fan will stop soon after. Depending on where in the PC the PSU is located and whether the PC case is made from metal or other material.

I'm not saying each and every cheap PSU will cause fire, many of them are known as Chinese firecrackers.


While a burning PSU destroys itself -- it might find some empathic companions for the trip towards Nirwana...


Guido


Desktop; i7-2600k, 8 GB mem., Win 10 Pro, BIAB 2017; RB 2017 - latest build
Laptop: i5-2410M, 4 GB mem, Win 10 Pro, BIAB 2017; RB 2017 - latest build