The unauthorised modification of an appliance by a dealer or gas practitioner invalidates the Safe Appliance Permit and makes the CoC that a gas practitioners’ issues for an appliance involving such a modified appliance invalid.  There may be warranty issues when the appliance needs repair, or an accident occurs involving a modified appliance and the insurance implications could be significant. An insurance company would be well within their rights to repudiate a claim, which could have severe financial repercussions.