Re: Can someone hold his breath in space?

Well, no - you're lungs would not "explode", but you probably damage them much the same way 
a scuba diver would damage their lungs if they came to the surface while holding their breath.  
Interestingly, your question is a pretty common one and rather than repeat everything here, the 
following link takes you to a NASA page with your answer:
 http://imagine.gsfc.nasa.gov/docs/ask_astro/answers/970603.html

-Steve