Hi friends. I have made a list of points based on my experience which needs to be checked before buying
Make sure the chimney is stainless steel made
Confirm whether the installation is free or not. Some vendor charge for installation.
Confirm the after sale service is available in your city or the person has to be called from another city.
The hose or pipe connection can be negotiated for free.
How much noise the chimney fan makes.
What is the capacity of the fan. Whether the chimney has to be manually cleaned or it has auto clean feature. Kutchina has those models