What precautions need to be taken when applying a food grade lubricant?

A foodgrade lubricant may be selected for a number of reasons: a desire to minimise risk as much as possible for the end client, the desire to meet the requirements of a critical control point approach (e.g.: HACCP) or of a standard (e.g.: ISO 22000) or regulation.
Whatever the reason for this choice, the machine's overall oil feed must be deemed permissible for accidental contact with foodstuffs. 
The permissible level for contamination as far as an NSF H1-registered product is concerned is 10ppm – i.e., 10 g per production tonne.  By extension, for a product that is not appropriate for accidental contact with foodstuffs, the permissible residual content is zero: 0 ppm. This also applies to products that are registered as NSF H2. 
This means that the facility has to be systematically flushed when switching to a food-grade lubricant. The procedure used should remove as much of the old lubricant as possible, depending on the type of equipment in question: gearbox, with or without oil circulation, hydraulic circuit, heat transfer fluid facility, compressor, air lubricators, etc.