One type of smoke detector must carry a label warning of the presence of a minute amount of a hazardous material. What kind of hazardous material?

The presence of a minute amount of a hazardous material in certain types of smoke detectors is associated specifically with radioactive material. Certain smoke detectors, particularly ionization smoke detectors, utilize a small amount of radioactive isotopes, usually americium-241. This isotope plays a crucial role in the ionization process that allows the detector to sense smoke particles in the air.

As a regulatory requirement, these detectors must include a warning label due to the potential safety implications posed by the radioactive material, even at low levels. Understanding this helps to identify why this specific hazardous classification is necessary for safety and compliance in fire safety equipment.

The other options do not accurately reflect the type of hazardous material used in the context of smoke detectors. Toxic gases, corrosive materials, and combustible materials do not typically make their way into the design and function of smoke detectors in the same manner as radioactive materials do.