Fireworks process buildings include any buildings in which pyrotechnic compositions or explosives materials are mixed, pressed, finished, or assembled. Outdoor pyrotechnic mixing areas (e.g., areas used for mixing flash or black powder) are included in the definition of fireworks mixing buildings and are therefore considered “fireworks process buildings” which are subject to the distance and weight limitations addressed at 27 CFR §§ 555.222 and 555.223. Fireworks process buildings do not include plant warehouses, office buildings, or other buildings and areas in which no fireworks, pyrotechnic compositions, or explosive materials are processed or stored. Further, ATF has determined that open outdoor areas used for assembly operations other than mixing would not fall within the definition of “fireworks process buildings” because the term “area” is only used for defining “fireworks mixing building”. Keep in mind that all pyrotechnic mixing and assembling operations in process buildings must meet the aforementioned distance and weight limitations in §§ 555.222 and 555.223. [27 CFR 555.11: definition of “fireworks process building”]