What substances can protect a worker from inhalation exposure? (Select two)

To effectively protect a worker from inhalation exposure, the chosen substance must act as a barrier or filtering mechanism against airborne contaminants. In this case, chemical vapors are considered because they can be managed or mitigated through personal protective equipment (PPE), like respiratory masks or respirators, which are designed to filter out harmful vapors from the air.

The other options—Injected toxicants, liquid chemicals, and dusts—do not serve this protective function. Injected toxicants enter the body through direct routes, such as injections, and do not provide a barrier against inhalation. Liquid chemicals, while they can exist in vapor form, do not inherently offer protection against inhalation without application of appropriate PPE. Dusts may pose an inhalation risk themselves, and thus are not protective but rather a hazard. Therefore, the selection of chemical vapors as a protective option hinges on the ability of PPE to interact with those vapors and reduce exposure effectively.