乾清门外两侧的10口大铀缸格外引人注目。大铜缸金光闪闪，在红色宫墙的映衬下，赤行富丽堂后皇，气热血甚壮。然而，这些大铜缸和大铁昔日皇宫却不是装饿用品，而是用来贮水的防火用具。缸内平时注潢汪水，随时可以灭火。到了冬季，为了防止结冰，专有内务府太监负责在缸外套上校风套保温并加盖，缸底还要烯起炭火，直到来年春暖时才撤火。故宫博物院成立以后，为防止缸内积水，在缸底均钻有漏水孔。

The 10 large uranium tanks on both sides of the Qianqing gate are particularly striking. The big copper tank is glittering with gold. Against the red palace wall, the empress of the red hall is very strong. However, these big copper tanks and big iron imperial palaces used to be fire-proof appliances used to store water instead of food. Water is usually injected into the cylinder to extinguish the fire at any time. In winter, in order to prevent freezing, the special eunuch of the interior government is responsible for the heat preservation and capping of the captain's air sleeve on the cylinder jacket, and the bottom of the cylinder needs to be filled with carbon fire until the next spring warm. After the establishment of the Palace Museum, in order to prevent water accumulation in the tank, water leakage holes were drilled at the bottom of the tank.