Four 55-gallon drums of 48 percent by weight aqueous hydrofluoric acid solution are stored in a warehouse on a single pallet. Does a threshold quantity of hydrogen fluoride exist?

At 1.15 g/ml, 55 gallons of solution weighs 527.85 pounds. At a concentration of 48 percent, the weight of HF in each drum is 253.37 pounds. The aggregate amount of HF, therefore, is 1013.5 pounds (253.37 pounds/drum x 4 drums). The threshold quantity of HF is 1000 pounds. Because the storage of the four drums on a single pallet is considered a single process, a threshold quantity of HF is present.