Fabric and paint are the primary collectors and retainers of odors.
1. Paint the inside
2. Clean or replace the carpet
3. Don't let the pets in the house until they have been bathed.
4. Use an ionic breeze type unit in each room where the pets reside.
5. Make sure all fabric materials are cleaned (professional fabric care, carpet cleaner), including sofas, cushions, pillows, comforters, drapes, etc.
Hope this is helpful.