What is the purpose of a tank vent?

A tank vent serves the critical purpose of allowing air to enter and exit the tank. This function is essential to maintain atmospheric pressure within the tank as liquid is added or withdrawn. When liquid is drawn out, a vacuum could develop if there is no venting, which can cause structural stress or potential damage to the tank. Similarly, when liquid is added, the vent allows displacement of air to avoid pressurization. Proper venting is crucial for safe tank operation and to prevent any issues related to pressure changes, ensuring that the tank functions efficiently and safely.

While some of the other options touch on aspects related to tank operation, they do not accurately represent the primary role of a tank vent. For instance, pressurizing the tank can lead to risks, and preventing overflow generally involves other mechanisms such as overflow lines or alarms rather than the vent itself. Filtering contaminants pertains to ensuring the quality of the liquids involved, which is also not a function of the vent. Thus, the correct understanding of the vent's purpose underscores its importance in facilitating safe and effective tank operation.