By default, the top level /feed/ RSS feed of your website contains everything. PowerPress creates a default podcast-only feed for you at /feed/podcast/ You can see this URL by going to PowerPress >> Settings, Advanced Mode >> Feeds tab, the URL is listed towards the top of the tab in the Podcast Feeds section.
You can also try selecting the "Do Not Enhance Feeds" option at the top of the Feeds tab. But that may not necessarily keep your podcast episodes out of the top level /feed/ RSS feed.