How long does it take to explore Orange Isle and Hunan Provincial Museum?

Generally speaking, the suggested sightseeing time of these two scenic areas is half day.
You can make full use of the time to visit one of these two attractions because you need to go back to the airport at least 2 hours in advance before the departure.
Upon landing, you are advised to consult the airport staff and see whether if they provide such half day tour.

Thank you for informing me it takes half-a-day at least to explore Orange Isle and Hunan Provincial Museum. They are certainly huge. As far as my research shows, the airport does not have half-day city tours for transit passengers. It is its plan to do so only as it is still liaising with the city tourism authority to organize free half-day city tours for transit passengers. I will just experience Maglev rides and leave early for Haikou during lunch hour.