Garoo

There are several cases of humans surviving exposure to vacuum worth noting. In 1966 a technician at NASA Houston was decompressed to vacuum in a space-suit test accident. He lost consciousness in 12-15 seconds. When pressure was restored after about 30 seconds of exposure, he regained consciousness, with no apparent injury sustained.

Why is there still a debate?

I’m not convinced of the dangers of explosive decompression, either — it seems to me that, unless your ship actually explodes or you’re teleported into space, the loss of atmosphere would almost always be a wind (as the air escapes from whatever contains it) rather than a sudden decompression.

Also:

yarchive.net

The best Earthly comparison is what happens to people who walk into a room containing a pure-nitrogen atmosphere. Such accidents happen occasionally in industry. Sudden loss of consciousness occurs within 10-15s, and death follows quickly. Stringent precautions have to be taken to prevent such accidents, because survival is rare – you get no warning that you’re about to keel over.

Wow. Only ten to fifteen seconds between the lungs being emptied of oxygen and the brain shutting down.