Generally speaking, ventless gas hearth systems are not prohibited in mobile homes outside of local code requirements, however, some ventless gas fireplaces may not be installed in a mobile home. In short, you would need to confirm that the model you are considering is approved for installation in a mobile home. This is normally stated in the first few pages of the product literature for any gas hearth system you would be considering. Before shopping for a ventless system, you would also want to check with your local code office to confirm that there are no restrictions on ventless gas hearth systems.
on December 5, 2019