In AC and S, Inc. v. Asner, 344 Md. 155, 174-75, 686 A.2d 250 (1996), the Court of Appeals provided a guideline for dealing with jury instructions as to exposure by non-parties. A factual defense may be based on the negligible effect of a claimant's exposure to the defendant's product, or on the negligible effect of the asbestos content of a defendant's product, or both. In such a case the degree of exposure to a non-party's product and the extent of the asbestos content of the non-party's product may be relevant to demonstrating the non-substantial nature of the exposure to, or of the asbestos content of, the defendant's product. But, a defendant would not ordinarily generate a jury issue on lack of substantial factor causation only by showing the dangerousness of a non-party's product to which the claimant was exposed. Ordinarily a defendant would have to follow up the evidence of exposure to the products of non-parties with evidence tending to prove that the defendant's product was not unreasonably dangerous or was not a substantial causal factor. Under these circumstances the proposition that the defendant's product is not a substantial cause may be made more probable by evidence tending to prove that the claimant's disease was caused by the products of one or more non-parties. See, e.g., Becker v. Baron Bros., 138 N.J. 145, 649 A.2d 613 (1994) (whether processed chrysotile in brake products posed a risk of causing mesothelioma in users was a sharply disputed issue of fact at trial, so that trial court erred in instructing as a matter of law that the products were defective without a warning). (344 Md. at 176-77)