Human Factors of Effective Warning Statements featured image

Human Factors of Effective Warning Statements

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Usable instructions for use (IFUs) for medical devices are more than step-by-step processes for users. They also must explain why the product should be used as described. Naturally, the ultimate goal of most readers of an IFU is to learn how to use the darn thing, but for products that present risks to their users (ahem, medical devices), it is absolutely critical that readers understand what those risks are. Writers of these instruction manuals need to make the explanations of these risks abundantly clear.

The typical method for communicating risks and hazards is the use of warnings, which are a common type of precautionary statement. Believe it or not, there are right ways and there are wrong ways to warn someone not to pour water over their new electronic device. Whether you thought you needed help or not, this article will summarize the human factors and a few need-to-knows of constructing effective warning statements.

Types of Precautionary Statements

First, let’s talk about the four precautionary statements. While the untrained eye may believe warnings and cautions to be synonymous, they simply aren’t.

DANGER – DANGER statements indicate a hazardous situation that, if not avoided, will result in death or serious injury. The signal word “DANGER” should only be used in these most extreme situations.

WARNING – WARNING statements indicate a hazardous situation that, if not avoided, could result in death or serious injury.

CAUTION – CAUTION statements indicate a hazardous situation that, if not avoided, could result in minor or moderate injury.

NOTICE – NOTICE statements are for important or helpful information but is not hazard related.

If you are interested in reading the official definitions of precautionary statements (which are very similar to those listed above), the American National Standards Institute (ANSI) standard Z535.5 can be found here.

Structure of a Precautionary Statement

Now that we know when to use which precautionary statement, we can break down the content of each statement into parts. An effective precautionary statement does four things:

  1. Starts with a signal word: DANGER, WARNING, CAUTION, or NOTICE.
  2. Explains the hazard and how severe it is, if applicable
  3. Instructs how to avoid the hazard, if applicable
  4. Explains what happens if the hazard is not avoided, if applicable

That’s quite a bit of information! Precautionary statements can be weak or ineffective because they fail to do one or more of those things. However, with such an explicit list of ingredients, warnings are much easier to write.

Here’s an example:

(1) WARNING: (2) Failure to dispose of used sharps properly can result in accidental needle sticks. (3) Always dispose of used needles in an appropriate sharps container immediately after the injection. (4) Failure to dispose of used sharps properly can result in serious injury or death.

This particular warning leaves no room for doubt. The reader gets information on the nature of the hazard, what to do about it, and specifically what can happen if the warning is neglected. What the user should or should not do is perfectly clear.

By knowing the various components of a precautionary statement, it makes the author’s job quite a bit easier. As long as each of those four boxes is checked, you should be good to go.

Other Helpful Tips Regarding Precautionary Statements

  • Avoid using too many warnings, if possible. Including too many precautionary statements can reduce the amount of attention paid to each one.
  • Place warnings at the beginning of the relevant section AND/OR before the step itself. The user could easily perform the step before reading the warning in question, which is obviously counterproductive.
  • Structure precautionary statements in a consistent way throughout your IFU. Inconsistent statement anatomy keeps the reader guessing and ultimately reduces readability.
  • Use precautionary statement pictograms like those outlined by the Occupational Safety and Health Administration (OSHA) to communicate further information about hazards.

To learn more, check out this video we made about the same topic!

Contact us to learn more about precautionary statements and the human factors of IFUs.

Anders Orn photo

Anders Orn Senior Human Factors Scientist

Anders Orn is a Senior Human Factors Scientist. He loves usability studies because he enjoys studying and learning from people. In his spare time, he can be found outside, on a mountain, or at home with his family. You can find Anders on LinkedIn here.