When installing fuel tanks inside buildings, per the International Fire Code, all tank vents should be taken to the exterior, except in the case of “protected” tanks (UL2085 listed tanks), which are allowed to have emergency vents terminated inside.
The section of the 2018 IFC related to tank venting can be found here. Below is an excerpt listing the requirements for emergency vents:
5704.2.7.4 Emergency venting. Stationary, above- ground tanks shall be equipped with additional venting that will relieve excessive internal pressure caused by exposure to fires. Emergency vents for Class I,II and IIIA liquids shall not discharge inside buildings. The venting shall be installed and maintained in accordance with Section 22.7 of NFPA 30.
Exceptions: 1. Tanks larger than 12,000 gallons (45,420 L) in capacity storing Class IIIB liquids that are not within the diked area or the drainage path of Class I or II liquids do not require emergency relief venting. 2. Emergency vents on protected above-ground tanks complying with UL 2085 containing Class II or IIIA liquids are allowed to discharge inside the building.2018 International Fire Code, Chapter 57.
Have a look at the pictures below. Can you identify the correct installation?