What aspect of respirator use is critical for ensuring safety?

The fit of a respirator against the face is critical for ensuring safety because a proper seal is necessary to effectively protect the user from inhaling hazardous airborne substances. If the respirator does not fit well, air can bypass the filter, which negates its effectiveness and exposes the wearer to harmful contaminants. Achieving a good fit means that the respirator can provide the intended level of protection, as it ensures that all inhaled air passes through the filter and not around the edges.

While other factors, such as the type of filter used, are important for matching the respirator to the specific hazards present, an inadequate fit renders those features ineffective. Color and cost may influence user preferences or compliance but do not directly impact the protective capability of the respirator. Therefore, ensuring a proper fit is paramount for safety in respiratory protection.