Holkham Paints FAQ said:I am having new windows / doors / sills installed in my house and the wood has already been ‘protected’ with tanalith or protim. Do I still need to use linseed oil?
These are anti-fungicidal chemicals, which have been applied under pressure to the timber to protect the wood from insect and fungus attack. In our experience Linseed Oil is the most effective, natural and healthy protection against rot. Tanalith has arsenic in it and it is likely that it will be banned in a few years on Health and Safety grounds, so it would be better to avoid its use.
If however your windows and doors have already been treated, then you will need to check the moisture content of the timber before applying the initial coat of linseed oil. If the moisture content reads 12-15% then it is OK to apply a coat of oil. If it reads above this level, then you should refrain from applying the oil and go straight onto applying the first coat of paint.