## Facts

- William Keith Johnson worked as an HVAC technician from 1996 to 2002 and completed formal HVAC training and extensive on-the-job training.
- Johnson obtained an EPA “universal” certification that allowed him to work on and purchase refrigerant for large commercial HVAC systems.
- Large HVAC systems commonly use refrigerant R-22; when exposed to flame or high heat during procedures such as brazing, residual R-22 can decompose into phosgene gas, which can cause serious lung injury.
- The potential formation and dangers of phosgene from heated refrigerants were generally known in the HVAC field and among manufacturers for decades.
- Material Safety Data Sheets (MSDSs) describing R-22 hazards were provided when Johnson purchased R-22 beginning in 1997.
- Johnson alleged that while brazing a refrigerant line on an evaporator manufactured by American Standard, he was exposed to phosgene and later developed pulmonary fibrosis.
- Johnson sued American Standard and others for negligence and strict liability based on failure to warn of the risk that R-22 could decompose into phosgene during ordinary service procedures.

## Issues

1. Whether California recognizes a “sophisticated user” doctrine that negates a manufacturer’s duty to warn.
2. Whether, under that doctrine, a manufacturer has no duty to warn when the plaintiff belongs to a professional class that knew or should have known of the relevant hazard (here, phosgene formation from heated R-22).

## Decision

- The California Supreme Court adopted the sophisticated user defense as a limitation on a manufacturer’s duty to warn.
- The Court held the defense applies when the plaintiff knew or should have known of the product’s hazard, including by virtue of membership in a knowledgeable professional class.
- The Court concluded Johnson was a sophisticated user with respect to the phosgene risk from heating R-22 during brazing.
- The Court affirmed the judgment for American Standard, upholding summary judgment on Johnson’s failure-to-warn negligence and strict liability claims.

## Legal Principles

- A manufacturer generally has a duty to warn of product risks, but there is no duty to warn of dangers that are obvious or generally known.
- The sophisticated user doctrine is a specific application of the “obvious or generally known” limitation: a manufacturer need not warn users whose knowledge of the danger equals or exceeds what a warning would convey.
- The defense turns on whether the risk is generally known to the relevant class of users; it is not limited to proof of an individual plaintiff’s subjective awareness.
- Where a sophisticated user knew or should have known of the hazard, the absence of an additional warning is not a legal cause of the injury because the warning would not have changed the user’s conduct.
- Policy considerations support the doctrine, including avoiding excessive warnings that reduce warning effectiveness and recognizing professional responsibility to remain informed about known industry hazards.

## Conclusion

California adopted the sophisticated user defense, holding that manufacturers have no duty to warn trained professionals of hazards that are generally known in their field; because an HVAC technician with Johnson’s training and access to industry safety information knew or should have known of phosgene risks from heated R-22, summary judgment for the manufacturer was proper.


Johnson v. American Standard, Inc., 43 Cal. 4th 56, 179 P.3d 905 (Cal. 2008)