On my breaths, if I use silence, it makes too sharp of distinction. If I use Amplify and dial it back to say, -25 it is OK at best. How do I take a recording of room noise, however slight, and lay it over the breath sound???
Steve made a noise-gate plug-in for Audacity which has the ability to attenuate , rather than completely remove , all the breath sounds, see … http://wiki.audacityteam.org/wiki/Nyquist_Effect_Plug-ins#Noise_Gate
If you must completely remove all the breath sounds, Auto-Duck could be used to patch a recording of room-noise into the dead-silences , ( although I’ve never actually done that though : it’s going to be difficult to create a seamless transition where one cannot spot-the-join ).