The breather hose works like a valve for the fuel tank and allows the air to enter the fuel tank but it won't allow fuel or fuel emissions to leave the tank

287520 (YTH 2042)(2007-01) (Sears) Yard Tractor

143186082 Craftsman 4-cycle Engine

Troy-Bilt: 754-04219

585152401 Craftsman Battery Cover Availability_Normally ships in 3-7 days The breather hose works like585152401 Craftsman Battery Cover Replaces 436216X428, 532436222, 532436223, 532446471, 583585901, 584633601 Fits Models Craftsman 917370930 Lawn Mower 917370931 Lawn Mower 917370932 Lawn Mower 917370933 Lawn Mower 917370934 Lawn Mower 917370935 Lawn Mower 917375920 Lawn Mower 917375921 Lawn Mower 917375922 Lawn Mower 944101761 Lawn Mower Husqvarna HU725AWDEX (96143012000) (2015 11) Lawn Mower: Consumer Walk Behind