carbon adsorbent is filled around insert 170 creating a hollow cylinder 184 of adsorbent between insert 170 and wall 171 of chamber 116 of course carbon is further added to fill both chambers 114 116 in adsorption mode of improved canister 110 vapors 22 flow through end cap 120 and are partially adsorbed in chamber 114 additional vapors 52 flow through chamber 114 crossover space 144 vapors 46 and are additionally adsorbed 54 in chamber 116 vapor flow 56 in the hollow cylinder shaped carbon region 184 around insert 170 is especially efficient in removing emissions because of an increased l d ratio air initially in canister 110 is expelled via atmosphere port 138 in desorption mode flow is reversed through the canister first a connection is opened between port 128 and engine 30 then vapors 32 are stripped from carbon in chambers 114 116 by atmospheric air drawn in through port 138 and are conveyed to engine 30 where they are combusted as noted above a benefit of improved canister 110 is the increased l d ratio in second chamber 116 making the unit significantly more efficient because chamber 116 is filled with carbon and settled along with chamber 114 manufacturing complexity and cost are reduced over the prior.