CLEA 1.06 uses the Jury model for the outdoor air shallow soil pathway (<1m) and an amended CLR-10 outdoor air model for deeper soils at >1 m (it is a long dull story as to why the EA got to here).
Try increasing your source depth for outdoor air to 1.01m to see if that gives the ratios you want. It may be something to do with the Jury model implementation.
Or it may be that the ADE from outdoor air is so small compared with indoor air (see below) that CLEA doesn't give you a number. Try just running the outdoor air by itself.
If you are after a source vapour SAC (vSAC) to compare soil vapour testing results against, the other way is to run in SAC calculation mode with indoor/outdoor switched on and then look at your media concentrations on your results outputs (these are the vSAC).
But I would not advocate straight calculation using the CLEA to give vapour outputs as CLEA 1.06 incorrectly (in my view) applies the Indoor Air Correction Factor (10 for benzene) to the soil vapour outputs (mg/m3) and soil outputs (mg/kg), instead of just to the soil outputs. For soil vapour outputs I would set CF=1 within CLEA 1.06.
For a default CLEA residential setting (source at 0.5m below foundation), our in-house CLEA model (benchmarked to 1.06, but using CF=1 for soil vapour outputs) gives a soil vapour SAC of 4.6 to 5.4 mg/m3 (depending on whether Qs is default or site specific) [CLEA 1.06 gives 46 and 54 mg/m3, which I wouldn't rely on with CF=10].
I would also say that it would be reasonable to ignore the outdoor air pathway if considering indoor air (the outdoor air soil vapour target would be an impossible >500,000 mg/m3).
At 0.1 mg/m3 benzene at soil source, CLEA estimates that your receptor would be exposed to 1.9 to 2.2% of the indoor air ADE (ignoring CF of 10).
Feel free to give me a call.
Peak Environmental Solutions Limited
Unit 10, Aston Ind Estate, Parsons Lane, Hope, Hope Valley, Derbyshire, S33 6RB
Tel: 01433 620030