Atmospheric-type storage tanks shall have capacities to accommodate which of the following?

• A. The need quantity plus space for thermal expansion
• B. The need quantity
• C. Capacity equal to double the need quantity
• D. Determined by manufacturer

Answer: (A)

Sizing atmospheric foam concentrate storage tanks means accounting for both the amount of concentrate the system needs and the space that must be left for thermal expansion. Foam concentrates can expand when they are heated, pumped, or agitated, so filling a tank to only the immediate need quantity risks overflowing as the liquid expands. By specifying capacity to hold the required quantity plus space for thermal expansion, you ensure there is always room for that expansion and you maintain reliable delivery to the system. This approach prevents overfills and keeps the system prepared for changes in temperature or operation. The other options either ignore expansion, rely solely on what’s needed without any allowance, or depend entirely on the manufacturer, which NFPA guidance does not support as the sole basis for sizing.