De-grease regularly, or else!
Please be advised:
Per GadgetGary, his neighbor's house burnt to the ground due to a grease fire in the exhaust ducting of just such an indoor grill. I believe the name-brand was the same.
Ammonia is perhaps the dest de-greaser. If you have a cat you MUST rinse with vinegar or lemon, in that the ammonia registers as urine to them and sends the message "This is a cat-box. do your business HERE."
As I always say..
EVERYONE is entitled to MY opinion...
(ducks and runs)