Gas sensors to 1-wire

This is good idea.
You can use this board: http://www.hobby-boards.com/catalog/product_info.php?cPath=22&products_id=91
There is also schema for ds2438 from this device: http://www.hobby-boards.com/catalog/links/ts3-r1/Humidity-Temp-Solar%20v3.2%20Schematic.pdf