When applying visual inspection to determine the cleanliness of equipment, manufacturers should establish the threshold at which the product is readily visible as a residue.

This should also consider the ability to visually inspect the equipment, for example, under the lighting conditions and distances observed in the field. Visual inspection should include all product contact surfaces where contamination may be held, including those that require dismantling of equipment to gain access for inspection and by use of tools (for example, mirror, light source, boroscope) to access areas not otherwise visible.

Non-product contact surfaces that may retain products that could be dislodged or transferred into future batches should be included in the visual inspection. Written instructions specifying all areas requiring visual inspection should be in place, and records should confirm that all inspections are completed. Operators performing visual inspection need specific training in the process, including periodic eyesight testing. Their competency should be proven through a practical assessment.