Theoretically, a resistance to ground of 1,000,000 ohms is considered capable of dissipating a static electrical charge. So why then does my safety program (and NFPA 77) require a resistance to ground of 10 or 25 ohms OR LESS, depending on the metal used in my system? (e.g. end-to-end resistance of a bonding wire should be less than 10 ohms for COPPER and less than 25 ohms for STAINLESS STEEL)
Well, to make this short and simple, the best way to explain it is the 10/25 ohms resistance is a VERY LARGE SAFETY FACTOR/MARGIN!
When a path-to-ground test is higher than the 10/25 ohm resistance, it is a very good indicator that our path-to-ground has some issues. And with repeated use of this bonding/grounding system, this resistance to ground is likely to only get worse.
For example, when a facility begins performing ANNUAL resistance testing of its flammable liquids grounding systems; those that are used daily will most likely fail to meet the 10/25 ohm limit. This failure does NOT mean we had unacceptable risks during our transfers; it is actually proof as to why we strive for a resistance of 10/25 ohms (e.g. that large SAFETY MARGIN).