Thanks Lobo for your help

I should have mention it:

• I don't have Blender and don't use any plugin but export (obj) to render in Octane stand alone.
• The last version of Octane integrate vdb file to render smoke. I tried with a sample I found in the Otoy forum and I'm impressed with the result.
• I'm now looking for a solution to generate smoke export (vdb format). Perhaps Blender could be the answer

If someone already tried or can make an export sample for me to see if it works in Octane I would be the happiest man...and perhaps a new user of blender! :-)