Question: I was arguing with my colleague about this matter (I'm not going to mention which side I fall on).

Would death be immediate in the vacuum of space? For example, if I was suddenly teleported into the vacuum of space would I die straight away? Or would I experience a suffocating sensation?

Answer: 
Nope, you wouldn't die *instantly*. While explosive decompression has never been tested on humans (for obvious reasons), the dangers of a vacuum have mostly to do with the pressure differential between your body and the now pressure-less void around you. The most fragile parts of the biological system would be the lungs and ears, and the instantaneous transportation would cause a severe case of the Bends if you were rescued quickly enough. You would pass out within a few seconds [stated by NASA when an experiment went awry](http://imagine.gsfc.nasa.gov/docs/ask_astro/answers/970603.html), and death might be from lack of oxygen to the brain, although after a few minutes everything bad starts to happen so nobody really knows what you would die of:

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> At NASA's Manned Spacecraft Center (now renamed Johnson Space Center) we had a test subject accidentally exposed to a near vacuum (less than 1 psi) in an incident involving a leaking space suit in a vacuum chamber back in '65. He remained conscious for about 14 seconds, which is about the time it takes for O2 deprived blood to go from the lungs to the brain. The suit probably did not reach a hard vacuum, and we began repressurizing the chamber within 15 seconds. The subject regained consciousness at around 15,000 feet equivalent altitude. The subject later reported that he could feel and hear the air leaking out, and his last conscious memory was of the water on his tongue beginning to boil. 
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If an astronaut were teleported into space without her spacesuit/helmet, she would feel a suffocation feeling, likely making breathing motions even though there is no air to breathe. She would also feel her sweat, saliva, tears, mucous, and any other water on her body boil off, though her body would maintain blood pressure, at least until her heart stopped. She would be unconscious within 15-20 seconds and dead within 90-120 seconds.