A series of pilot-scale pool test fires simulated an idealized fire accident in a storage tank containing low-sulfur No. 6 heavy fuel oil (LSFO6). This work demonstrates that the combustion characteristics of LSFO6 and shows that fire-related emission factors (EFs) of 16 USEPA PAHs during pool fires very much depend on the scale of oil pan diameter (D). Over the range studied (D = 20-60 cm), the combustion characteristics, (i) fuel mass loss rate, (ii) heat flux and (iii) ratio of CO/CO2 as time-weighted averages have positive linear relationships with D, but the combustion efficiency is a negative linear function of D. The sum of 16 PAH EFs has a negative linear function of D, while the overall vapor-particulate partitioning coefficient of 16 PAHs has a positive linear function of D. Most benzo(a) pyrene-toxic equivalents (BaPeq) for a given pool scale arise from high-molecular-weight PAHs. However, the maximum total BaPeq occurs at pool fire scale of D = 40 cm. The scale of burning causes no significant variation in PAH source identifications in terms of the defined molecular diagnostic ratios. Further researches on large-scale pool test fires are needed to validate whether the applicability of pilot-scale studies will be acceptable to the relevant oil tank fires in industries.