For VIEWERS (i.e. regular attendees):

Business Hangouts runs basically everywhere, from  Windows desktop or Windows mobile to Chrome OS, Android, Blackberry or Apple iPhone, iPads or any iOS device or Mac device etc, with basically any HTML5 browser such as Chrome, Firefox, Safari, IE 10 or above, Opera, etc. Obviously you need your speakers ON to hear the presenters. In some rare cases, if YouTube SAFETY mode is turned on, you may have to turn it off from the home page (bottom of the page).

For Hosts and Guests or other Speakers :

System requirements for Hosts and other Speakers who need to be on the filmstrip are nothing more than those from Google for Hangouts:

Audio: Please make sure you mute yourself when you are not talking, and use earbuds or headsets for a better audio experience both for yourself and for the rest of the attendees.

For more information: FAQ