We recommend doing research on what bedding works best in your home environment for comfort and respiratory health. For example, our rats here, with studying their individual needs, specific care, careful breeding, and placing health first, are not experiencing "common" health issues that we have read about in rat care forums.
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. For your consideration, many people are turning to kiln-dried pine bedding for rat comfort and freshness.