M-8 and M-9 tape with a positive reading may indicate the use of what type of agent?

A positive reading on M-8 and M-9 tape is specifically indicative of the presence of certain chemicals, which is why selecting a chemical agent is the correct answer. M-8 tape detects liquid chemical agents such as nerve agents (e.g., VX and Sarin) and blister agents (e.g., mustard gas). Although M-9 tape is used to identify the presence of certain chemical agents as well, it is primarily designed for non-persistent agents that might be encountered in a CBRNE (Chemical, Biological, Radiological, Nuclear, and Explosive) incident.

In this context, biological agents would not produce a reading on either tape, as these agents typically require different detection methods and equipment that analyze for biological contaminants rather than chemical. Nerve agents are indeed classified as chemical agents but are a subset of the larger category of chemical agents. Radiological agents also would not provide a reading since M-8 and M-9 tapes are not used for detecting radiation; they are designed exclusively for chemical threats.

Thus, the identification of a positive reading aligns directly with the detection of chemical agents, emphasizing the importance of understanding the specific capabilities and limitations of the detection equipment used in various hazardous situations.