When is a Warning Defective?


So, you may ask, how can a “warning” be broken or defective? As is well known, engineers in considering hazards and safety in a product must follow what is commonly referred to as the “Engineering Hierarchy.” This is because safety is never optional. The hierarchy is as follows:

  1. Design out the hazard from the product.
  2. If the hazard cannot be designed out, the engineer must guard or contain the hazard so as to protect a user of the product.
  3. If the hazard can neither be designed out nor guarded or contained, then a warning must be provided.

When faced with a product where the engineer must warn about the product, the warning must contain two essential elements in order to be effective from an engineering perspective. First, the warning must clearly explain the hazard and second, the warning must also clearly inform the user of the product what specific and precise action is required in order to eliminate or significantly reduce the likelihood of injury or death from said product. A simple hypothetical example of such a warning might be:

“Risk of Explosion: Do not bring these fireworks within ten feet (10 feet) of an open flame.”

The same warning would be defective, from an engineering perspective, if it read:

“Risk of Explosion: Do not bring these fireworks too close to an open flame”

Clearly, the second warning does not provide information on how to eliminate or significantly reduce the risk of an explosion when handling and using the fireworks.

The following texts are reference materials which may provide the reader with further information on what information is necessary in a warning:

  1. Handbook and Standards for Manufacturing Safer Consumer Products, June (Revised May 1967) by United States Consumer Product Safety Commission;
  2. Safer by Design: Reducing Hazards through Better Design, American Society of Safety Engineers, February 1998;
  3. Designing Safety into Machine, Journal of the American Society of Safety Engineers, September 1998;
  4. Safety through Design, National Safety Council, 1999, Chapter 2; and
  5. Engineering by Design by George Dieter.

Review of many automobile owner’s manuals shows a common product, an automobile, where a defective warning is exists. An example of such a warning found in many automobile owner’s manuals reads as follows:

Seating Position: Sitting too close to an air-bag storage compartment or placing hands on it is extremely dangerous. Air bags inflate with great force and speed. Serious injuries could occur if someone is sitting too close. The driver should always hold only the rim of the steering wheel. The front seat passenger should keep both feet on the floor. Front seat occupants should adjust their seats as far back as possible, always sit upright against the seat backs and wear their seat belts properly.”

The introduction to this manual informs the reader that a warning caption means:

“A WARNING indicates a situation in which a serious injury or death could result if the warning is ignored.”

However, this warning fails to define for the reader of the owner’s manual what distance, in terms of actual inches or feet or some other metric, “sitting too close to an air-bag storage compartment” actually means. This warning indicates to the reader that a grave danger is present while seated in either of the front seats. However, it utterly fails to give the driver of the automobile any specific guidance as to safe distances in inches, feet or other metric, or to define how to sit a safe distance from, for example, the steering wheel/airbag. The warning gives no specific instructions for a driver of short stature how to avoid serious injury or death while still being able to safely reach the automobile’s control pedals.

Owner’s manuals provide instructions and warnings concerning the adjustment of the steering wheel tilt. However, these same manuals, in general, provide no information for a driver of short stature to place the steering wheel in its lowest position when sitting close to the steering wheel. Such a tilt position of the steering may reduce or minimize hazards associated with the deployment of the driver’s side airbag when a driver of short stature must sit close to the steering wheel of an automobile in order to safely reach the brake and gas pedals.

In hazard risk analysis, the engineer is required to identify hazards in the environment in which the product is used. The engineer must then evaluate the injury potential of those hazards. Once a hazard of serious injury or death is identified, the engineer is required to take steps to either eliminate or reduce the risk of injury. This is because public safety is paramount and safety is not optional. The engineer then approaches the hazard by applying the hierarchy of corrective action; these general hierarchy principles bear repeating and are as follows:

  1. Hazard Elimination by Design. When feasible a hazard in a mechanical design must be designed out.
  2. Guarding and Enclosures. When a hazard cannot be designed out of a product, then it must be guarded or enclosed.
  3. Safety Warnings and Instructions. When a hazard can neither be designed out nor guarded or enclosed then warnings and instructions must be provided so that the user may successfully avoid or minimize the risks associated with the hazard.

Contrast the information sited above and applicable to the driver of an automobile with the information provided to the front seat passenger of the same automobile, who is warned and instructed to do the following:

“…keep both feet on the floor. Front seat occupants should adjust their seats as far back as possible, always sit upright against the seat backs and wear their seat belts properly.”

This instruction clearly illustrates how to successfully avoid injury to the feet by not placing them on the dash and air-bag compartment cover. The instruction also indicates to adjust the seat as far back as possible (from the air-bag compartment), the appropriate manner in which to sit in the seat and the equipment that should be worn in order to minimize risk of an injury.

Owner’s and user’s manuals of any product, decided upon by an importer to be brought into the United States and sold and distributed in the United States market has in all probability already been designed and tested by the foreign manufacturer in some manner. The only remaining element of the design hierarchy which could and should be employed by the importer of a product into the United States market is the development of an owner’s manual which provides a warning and specific instructions (which includes a metric) regarding how to successfully avoid or minimize any significant risk of injury from use of the product due to its inherent and unavoidable hazards. Since all owners and user’s manuals for products should consider the United States citizen when the product is imported and distributed for use in the United States, the importer of the subject product should provide the information and metrics necessary to use the product in the safest manner possible. Owner’s manuals are always under the ultimate control of a United States importer, and can easily be modified or supplemented at little to no cost.

For further information regarding what a warning should contain, as a minimum, the reader may wish to consult product trade organizations’ voluntary standards or ANSI Z535.4-1991 and in particular paragraphs 2.1, 3.1, 4.7.2, and 4.11

M. Ezra, PE, Certified Safety Engineer, State of Missouri