Can regular (normal) venting serve as emergency venting if it is large enough?
A. Yes. Part 160 rules reference NFPA Standard #30 for determining the size/capacity of emergency venting. NFPA #30 allows all vent openings present on the storage tank (normal and emergency) to be credited when determining the available venting capacity for the tank. The required capacity of emergency venting is dependent upon the size of the storage tank (with larger tanks requiring more emergency venting capacity). This results in smaller tanks sometimes being able to comply with emergency venting requirement simply by the size of the normal vent piping placed on the tank. Essentially, the code is recognizing that the venting capacity offered by the normal vent that is designed to allow the tanks to breathe during filling or off-loading operations, is sufficient to provide venting of vapors under emergency conditions. Caution should be used however when installing an aboveground tank installation that does not present an emergency vent, separate from the normal vent. While indeed th
