This report has been written to answer questions about the feasibility of performing the tests described in the ISA standard for chlorine gas detection instruments (ISA-92.06.01-1998). The report discusses two questions; the first is the availability of a chlorine gas supply of sufficient accuracy and precision for performing the tests@ and the second is the viability of testing a gas detection instrument with chlorine under a variety of humidity conditions. The report surveys the available chemical literature@ presents experimental and calculated results of humidity testing@ and summarizes information on test gas generation and analysis.