We recommend reading about what bedding works best in your home environment for comfort and respiratory health. For example, our rats here are not experiencing "common" health issues that we have read about in rat care forums, and we use what we recommend below.
Some rats may experience "new home sneezes," a term popular in internet searches, but finding the right combination of your home's unique environment to the rats' bedding is critically important.
Some people are turning to higher-heated than kiln-dried pine bedding for rat comfort and freshness. Our favorite is as described above or Aspen shavings for absorbency, safety, and pet comfort.