Which of the following is NOT listed as an explosive odor?

Heroin is not classified as an explosive odor because it is a narcotic drug, rather than an explosive substance. Unlike the other options, which include materials and compounds that are specifically associated with explosives, heroin does not have explosive properties or characteristics.

C4, smokeless powder, and ammonium nitrate/fuel oil (ANFO) are all known for their ability to produce explosive reactions and are recognized for their distinct odor profiles associated with those properties. C4 is a plastic explosive with a specific scent, smokeless powder refers to a type of gunpowder with a relatively low odor compared to traditional black powder, and ANFO is a widely used explosive made from ammonium nitrate and fuel oil, also recognizable by its characteristic odors.

In contrast, heroin's properties do not relate to explosives, and it is primarily studied and regulated in the context of drug enforcement rather than safety protocols for explosives. Therefore, it correctly stands out as the option that does not belong on a list of explosive odors.