If you are going to use linseed oil at all, and are worried about any contaminants, why not just use flax oil? It is available in places like GNC. Isn’t linseed oil just flax oil under another name? I have hated the smell of linseed oil since my first oil paint set as a small kid. Ack! 
I actually find the scent quite pleasing 
I also like the smell of linseed oil.
I think the smell of the oil and the resinous smell of the blackwood complement each other nicely.
–James