ABSTRACT
Since much of the equipment is constructed along similar lines, this chapter describes general types of instruments and explains their theory of operation and use. It identifies special features offered by some manufacturers and discusses purchase options and considerations which may provide an advantage in confined space operations. Rapid advances in the field of electronics have spawned a proliferation of instrumentation that can be used to evaluate confined space atmospheric hazards. However, it can all ultimately be divided into two categories: direct-reading instruments and indirect-reading instruments. Regardless of the type of instrument, users must be aware of three important concepts: interference from materials other than the substance of interest, the effects of instrument response on measurements and the difference between accuracy and precision. Technical specifications outlined in instruction manuals and product literature describe an instrument's capabilities and limitations.
