As Chapter 9 noted, if you can design a hazard out of a product, you have no need to warn, because nothing is left to warn about. But not all hazards can be designed out. And even if a hazard can be guarded, you may still need to warn against removing the guard or operating the machine without the guard in place. Most products have at least some residual hazards that require warnings. How can you be sure your product’s warnings work effectively to help keep your users safe? This chapter will help you answer that question. While most of the information in this chapter is presented in terms of on-product warnings (usually labels), much of the information is applicable as well to warnings used in other contexts, including safety bulletins, manuals, packaging, and other product materials.