I know the validity of OAK's are a big topic on these forums and I for one am still on the fence. I did call my dealer today to discuss the need for an OAK and I just about finished the question when I was told there is ABSOLUTELY no reason to install an OAK except for situations where air flow is a problem (lazy flame) due to improper installations by DIY'ers. She clearly stated to me that heating zero degree air makes no sense and will reduce heat output and lose efficiency. Makes sense to me. She also stated that her business could make a lot more money if they recommend installing an OAK on all their pellet stove purchases but choose not to because they want to be honest and up front to their customers that an OAK has no advantages. These are her words not mine. Just thought I'd share that.