be exposed to liquid fuel during a lawn mower u201c roll over u201d situation canister 32 has a housing 42 containing a carbon bed 44 as suggested in fig5 and 6 and is sized to fit into a canister receiving cavity provided under shroud 30 in power source 14 as suggested in fig1 housing 42 is formed to include an interior region 400 containing carbon bed 44 an atmosphere orifice 401 opening into interior region 400 and a tank and engine orifice 402 opening into interior region 400 as suggested in fig5 and 6 in an illustrative embodiment housing 42 includes a cylindrical sleeve 423 interposed between first and second end closures 411 412 as suggested in fig3 a and 5 it is within the scope of this disclosure to provide sleeve 423 with any suitable length and shape and form end closures 411 412 to mate with sleeve 423 one end of sleeve 423 is formed to include atmosphere orifice 401 and another end of sleeve 423 is formed to include tank and engine orifice 402 canister 32 is configured to allow both fuel tank fuel vapor and atmospheric air to pass through carbon bed 44 canister 32 is configured to u201c clean u201d fuel vapor 46 vented from fuel tank.