For 20 grams of heroin, what is the predicted dissipation rate without air current within 30 minutes?

The dissipation rate of a substance like heroin, especially in scenarios without air movement, is influenced by several factors including particle size, environmental conditions, and the ability of the substance to evaporate or disperse. For heroin, the predicted dissipation rate in an enclosed space without air current is notably low due to the heavy and somewhat sticky nature of the drug.

Considering the details given, the range of about 1 to 1.5 feet reflects a reasonable assessment of how heroin would spread in a still environment over a half-hour period. This involves factors like gravity, which causes the substance to settle rather than disperse widely, as well as the physical characteristics of heroin that limit its vaporization.

Thus, the prediction aligns well with studies on drug dispersal in confined spaces, demonstrating that the low dissipation figure is more realistic compared to the other available options, which suggest a far greater spread than is practically observed for this type of substance under the specified conditions.