Improper venting can cause several concerns:
Firstly, any hollow section must be vented to allow complete flooding of the cavity with zinc and the expulsion of any trapped air. Failure to allow this will result in black spots or non-coated areas inside the section ultimately resulting in a non-conformance. Similarly, many open types of material must be properly vented to ensure a proper galvanizing job. Examples of proper venting and draining are shown below.
Secondly, if a sealed, hollow section is submerged, the trapped air will heat up and expand. This expansion can cause enough pressure in the product to split the steel and cause an explosion putting all plant personnel at serious risk.