When conducting gas related reactions, controlling the pressure in the vat can become very troublesome. If the ventilation pipe is directly opened, it will reduce the required gas molecules. Adding a one-way ventilation pipe for the vat can better control the air pressure (whether it is exhaust or suction)

While 0.1.0 will make some sort of pressure-release valve possible with Redstone, I agree it would be useful to have a simpler way of doing it too. In any case the way the Vent currently works needs redoing.