Which hazard pictogram indicates a respiratory sensitizer?

The health hazard pictogram is the correct choice to indicate a respiratory sensitizer. This pictogram features a silhouette of a person’s head with a star shape inside the chest area, symbolizing hazards related to serious health effects. Respiratory sensitizers are substances that can lead to respiratory allergies, making this pictogram suitable as it warns about potential health risks associated with chemical exposure.

In contrast, the flame pictogram represents flammable materials, while the flame over circle pictogram signifies oxidizers. The exclamation mark pictogram indicates general hazards such as irritants, skin sensitizers, or narcotic effects, but it does not specifically denote respiratory sensitization. Therefore, the health hazard pictogram is the most appropriate representation for respiratory sensitizers, emphasizing the potential health issues related to inhalation exposure.