Blowdown drums are a primary component of the safety recovery system and are used to collect overflow of process liquids and gases. They are usually kept at very low levels or completely empty but can be filled very rapidly at high pressures. During a pressure-relief at some stage of the process, hydrocarbon liquids and gases rapidly pass the drum, causing it to rapidly go from empty to full. The blowdown drum’s purpose is to contain and release its content in a safe manner, preventing potential personnel injury as well as plant and environmental damage. This application is thus safety critical and requires highly reliable level measurement devices with the appropriate safety integrity level.