Halloran (plaintiff) was an auto mechanic who used cans of refrigerant to service car air-conditioning units. The refrigerant he used was packaged and sold by Virginia Chemicals (defendant). Halloran was a very experienced mechanic, having serviced hundreds of air-conditioning units using thousands of cans of the refrigerant. When Halloran found it necessary to accelerate the flow of the refrigerant, which was often the case, he would heat water in a coffee can and put the can of the refrigerant inside the coffee can to warm it up. On one occasion, as Halloran warmed up a can of refrigerant, the can exploded, injuring Halloran. As a result, he brought a products-liability action against Virginia Chemicals. Warnings on the cans of refrigerant cautioned against using an immersion coil to heat them. Virginia Chemicals sought to introduce evidence that whenever Halloran warmed up a can of refrigerant, he always used an immersion coil. The trial court did not allow this evidence and the appellate court affirmed. Virginia Chemicals appealed.