The function of the exhaust manifold:

When gas overflows in the system, it rises along the pipeline and accumulates at the system's high point. The exhaust valves are typically installed at this high point. As the gas enters the valve cavity and accumulates above the exhaust valve, the pressure increases within the valve. When the gas pressure exceeds the system pressure, it causes the water level in the cavity to drop. The float descends with the water level, opening the exhaust port. After the gas is exhausted, the water level rises, and the float ascends with it, closing the exhaust port. When a vacuum is created in the system, the water level in the valve cavity drops, the exhaust port opens, and since the external atmospheric pressure is greater than the system pressure, air enters the system through the exhaust port, preventing the harm of the vacuum.