Time it takes to reach temperature equilibrium after exposing pre-heated air inside container to ambient (cooler) air

I have a closed container filled with heated air (50C). This container has a lid, and when the lid is opened, the heated air inside the container is exposed to ambient (cooler) air. Is there a way to find out how long it takes for the air inside the container to reach ambient temperature? Conduction and radiation can be ignored. 

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