According to the Code for Food Safety Operation in Catering Services, a metal grid or net cover with a mesh less than 10 mm should be set at the outlet of the drainage ditch to prevent the invasion of rats. The length and width are about 5 mm. Rat-proof net: 40 mesh (aperture less than 6 mm) barbed wire should be installed at various pipe orifices such as warehouses, windows, exhaust fans, ventilation holes and drainage holes. A movable baffle with a rat net can also be installed at the sewer outlet, and the diameter of the iron wire of the iron net should not be less than 65438 0 mm.
The hole diameter of the mousetrap installed at the exhaust fan is allowed to be less than 13mm, so as to avoid the mesh being too small and easily blocked by smoke.