Direct Vent Post Purge

Customer has a De Dietrich GT116A with Direct vent exhaust but takes air from the space. Recently on a gusty day, he noticed a strong exhaust smell in the space.

He watched the boiler run through a call for heat. He said while it was running it sounded good but when it shut down a puff of smoke came out of the intake port. He shut the power to the burner off and I'm going to address it this week. Fortunately he has a backup heat source.

He took some pics of the burner for me including with the cover off and there is no post purge control card installed. Shouldn't there be Post purge on all direct vent installations? this sounds like a recipe for a CO poisoning.

The burner is a Riello BF5 with the air intake post on the top but no piped intake air.