Not less than 40 seconds.
Warehouse airtightness: the use of positive pressure determination, the pressure from 500 Pa to 250 Pa time of not less than 40 seconds.
The earliest age of the ground grain silo is Zhejiang Hemudu site unearthed "pole and rail" grain silo, the silo is also full of rice, according to evidence that 7,000 years ago, is the earliest discovery of the south of the grain storage facilities. Larger scale, the earlier years on the ground when the granary in Gansu Province, a large pan of the city excavated "big square disk" granary. Dafangpan City, also known as the river warehouse city, 60 kilometers from Dunhuang City, about 20 kilometers from the Yumen Pass. This warehouse was built in the Han Dynasty, until the Wei and Jin dynasties has been the western border defense munitions warehouse.
"Big square plate" granary for the rectangular, east to west, east to west length of 132 meters, north to south width of 17 meters, the highest point of the existing wall is 6.7 meters, the structure of the wall for the rammed earth. Warehouse room has 3 rooms, 42.5 meters long, 14.5 meters wide, wall thickness of 1.5 meters, south direction of each open a door. In the more complete preservation of the north wall of the hamlet, the upper and lower are small triangular holes, each granary upper 3 lower 5, staggered, may be ventilation holes.
In the remains of the south warehouse wall, from the few remaining small holes can still be seen, its arrangement is symmetrical with the north wall. The barn was built on a natural earthen platform more than 2 meters higher than the local riverbed, and there were significant enclosures outside the barn walls in the east, west and north directions.
In addition to the excavation of the medieval ware in addition to the cottage warehouse and building warehouse, round warehouse, etc., these medieval ware in the granary, most of the ceramic, there are also wooden. Pottery granary, the vast majority of the Han Dynasty cultural relics, out of the land more in the north around. Wooden grain silos are less. Over the years, the excavation of the medieval grain silo in addition to the production of different materials and shapes, the vast majority of the complete doors and windows, ventilation holes, grain outlets, rodent-proof structure, moisture-proof structure, and so on. In addition, in some of the excavated stone or brick carvings have been found on some granary modeling.