Your aircraft has an exhaust manifold type heating system. The exhaust manifold is periodically inspected to avoid

Explanation

Exhaust-manifold (shroud) cabin heaters warm outside air by passing it around the exhaust; a crack in the manifold can let exhaust gases, including carbon monoxide, into the cabin air. The periodic inspection is aimed at that carbon monoxide risk, not at comfort issues like overheating or a cold cabin.