Read the PL thread DZ linked to.
The laser is the "70mw" module from DX (It burns paper however so I think it's overacheiveing)
And no, it's not a spec of dust or smoke and the right timing, that little ball of light floated in there for around a minute and a half, which gave me time to get those pics. The first one shows a much more realistic size of the trapped particle, but in real life it is just a tiny point of light.
Is this not the method being used by some in an attempt to create 3d mid air holography? Also how many mW is that laser?