Licensed Professional Engineers



A newsletter dedicated to keeping attorneys informed of the technical side of product liability cases.

Issue 70: Summer 2018

Warning Label Advances

By John L. Ryan, P.E.

© 2018 M.A.S.E. LLC

Warning label design has been refined over the years, and a new wave of change in warning labels is being seen, especially in foreign countries. The use of photographic warning labels may result in greater attenuation of warning labels, and ultimately greater warning compliance levels. Research indicates that warning compliance is affected by how dangerous product users think the product is. This issue of Forensic Clues examines some research relevant to improving warning label effectiveness by increasing the perceived hazardousness level of the product and using photographic images.

Research on Photographic Warning Labels

Canada has been using photographic warning labels on cigarette packaging for many years. A study of this, entitled “Evaluation of New Warnings on Cigarette Packages” (2001), explains an extensive research project measuring the effectiveness of new photographic warning labels against more traditional warning labels. This study found that photographic cigarette warnings do work. Specifically, it was found that smokers who read the photographic warning were more likely to quit smoking, attempt to quit smoking, or reduce the amount of their smoking.


 Examples of photographic warning labels on cigarette packaging

Effect of Perceived Hazardousness

A study by K. Friedmann, entitled “ The Effect of Adding Symbols to Written Warning Labels on User Behavior and Recall” published in Human Factors in 1988 discusses perceived hazard and its impact on warning compliance. His literature review includes a study by Godfrey and Laughery that showed by survey research that the likelihood of noticing a warning is inversely correlated to the product user’s familiarity with the product. Friedman performed experiments that found a positive correlation between the perceived hazardousness of a product, and not only reading the warning but also following and later recalling the warning. Warning compliance in this study was based on whether or not the participants donned appropriate personal protective equipment.

What Influences Perceived Hazard Level?

Wogalter, Jarrad, and Simpson describe in their article “Influence of Warning Label Signal Words on Perceived Hazard Levels” the impact of signal words on perceived hazard level. They found that signal words raise hazard perception. The signal word “lethal” was found to increase hazard perception more than “caution”, “warning”, or “danger”. They also found that younger participants rated products more hazardous than older participants.


Research has shown that warning labels using pictorials communicate large amounts of information quickly, and that symbols are advantageous in situations where written warnings may not be understood, whether due to poor vision, low verbal skills, or inadequate grasp of the language of the warning. Some studies indicate that symbols are better comprehended when some sort of context is also provided, but there is research that contradicts this.

How Does this Influence Warning Design?

While additional research will provide more insight into optimal warning design, some conclusions can be made based on the available research. If a product user believes a product to be hazardous, he or she will have a greater likelihood of attending to a warning, reading it, and following it. Photographic warning labels increase warning compliance, which is likely in part due to the increase of the perceived hazardousness of the product due to the photographic warning. The use of photographic warning labels could be expanded to many types of warnings, including machine and product hazards. Photographs or pictorials of a person being injured using a product would make the danger seem more real. There would be less interpretation required with a photographic warning label. Written warnings must be read and processed and applied to the situation. The meaning of pictorial warning labels must be interpreted, and studies have shown that misinterpretation of pictorial warning labels is common.

Example of photographic warning label for machine hazards

Is a Product Defective without a Warning?

The hierarchy of design is a fundamental engineering design concept where hazards are mitigated using the most effective means first. Elimination of the hazard is the most effective method of hazard control. The next most effective method of hazard control is to neutralize the hazard. Neutralizing the hazard involves using guarding techniques to protect people from the hazard. The next most effective method of hazard control is warnings. Warnings should never be used as a primary source of hazard control, however, unless it is impossible to eliminate or safeguard the hazard. Most hazards can be eliminated or safeguarded. The next most effective method of hazard control is to train product users on proper operation and to encourage safe working practices in an attempt to prevent injuries. Protective equipment is a last resort method of hazard control. This method should only be relied on when all other methods cannot be used. While attorneys and lay persons may focus on the need for warnings, there is often a much more effective way to mitigate the hazards of a product or machine. The main issue is whether product/machine hazards were safeguarded in the most effective manner.

How We Can Help

At MASE, we can determine if an accident was influenced by a poor warning, and we can identify if the product was defective due to a lack of safeguards, and identify what safeguards or design changes would have prevented an accident. We offer full service mechanical engineering expert witness services from inspection to trial testimony. Call us at (855) 627-6273 or email us at


We offer full service mechanical engineering expert witness services from inspection to trial testimony. Call us at (855) 627-6273 or email us at


What We Can Do For You

Provide mechanical engineering expertise for your product liability case

Help you decide on whether to take a case—we’ll give you a free, no obligation case assessment just call us at (855) 627-6273

Perform detailed and thorough engineering analysis of products involved in accidents

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Design solutions to product hazards that are left unguarded

Please call us to discuss any questions you have about unsafe products. (855) 627-6273

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