If there is something like smoke backing up into the home or some sort of functional issue, they need to have an inspection performed.

Ok, thank you. In order for us to provide you with a long term solution, one that we can stand behind, we need to do our due diligence and conduct an inspection of your entire venting system before we can provide you with an estimate. You may have underlying, potentially dangerous conditions that are causing the problem that you are seeing.

Does that make sense to you?