If the helmet is scaled up exactly 98 times, it will be the right size to fit a human head. However, I couldn't help but notice some problems with the model... Not trying to bash your work; you did an incredible job getting this print-ready.
You added part of the helmet to the faceplate... It should be attached to the main bulk of the helmet.
http://i262.photobucket.com/albums/ii86/hackmandude12/compare_zps88hvqpus.png
There is a curved part on the lower jaw that wouldn't allow the faceplate to sit in correctly, also. This could easily be fixed by filing it down , but the problem up above is really the only thing of concern.
http://i262.photobucket.com/albums/ii86/hackmandude12/jawprob_zpsf16xceqx.png
But again, you did a great job getting this 3d print-ready. Very good work.