This document describes practical and cost-effective monitoring approaches for using metal impurities in carbon nanotubes (CNTs) as indicators of their presence in the workplace. Its goal is to supplement the “toolbox” of existing methods available for risk assessment and exposure mitigation. Advice on sampling techniques and off-line analysis will assist the occupational hygienist to identify situations where metal impurities in CNTs can be applied as a sensitive but qualitative indicator of the presence of process-related releases of CNTs in the workplace. Limitations are identified which place the CNT tracer strategy in the category of a sensitive but qualitative (semi-quantitative) indicator of the presence of process-related releases of CNTs in the workplace. Qualitative evidence provided by monitoring CNT tracers may be useful to evaluate the effectiveness of clean-up and engineering control measures, and to assist in distinguishing CNTs from non-CNT sources of elemental carbon (such as diesel soot).