Bubblers are specifically designed to maintain an inert atmosphere within reaction systems. Since splashing is common, double, gas, horizontal, mineral oil, and nitrogen bubbler pipes are safer than the traditional mercury fill. If the pressure builds to exceed that of the laboratory atmosphere, excess gas will travel down the glass pipe, bubble, and eventually escape through the hood opening. If the pressure is less though, the contained liquid in the glass bubblers will rise to stop additional air from entering.