When it got too hot in the open area, the volleyball players moved to the cool hall.

When it got too hot in the open area, the volleyball players moved to the cool hall. Will they have to pump up the ball or let some of the air out of it? If necessary, why?

They will have to pump up the ball, because in a cold room, the ball and the air inside it will cool, and the pressure on the walls of the ball will subside, and it will lose its shape. When heated, all bodies expand, and when cooled, they contract. Therefore, in the room, the pressure in the ball will decrease, it will need to be pumped up, but do not overdo it so that it does not burst, because back on the street, the pressure in the ball will rise again due to heating.