It's not very scary but "The Asphyx" is very entertaining in an E.C. comic books kind of way. It reminded me a lot of one of the better stories from the Amicus anthologies but is, of course, considerably longer. In many ways it is a bit too long and some of the dialogue is slightly annoying but everything is well filmed.
The big similarity between the ending of this and "The Green Mile" is probably not accidental as I'm sure Stephen King has seen this too.