A variety of electronic direct-read instruments are available for measuring the concentrations of indoor air contaminants. Such instruments allow the operator to obtain real-time or quasi-real-time measurements of gas, vapor, or paniculate matter concentrations. Various sampling methods available for conducting indoor air quality measurements of common chemical contaminants are discussed. As with chemical contaminants, the conduct of bioaerosol measurements should be based on clearly defined objectives and a standardized measurement protocol to ensure relatively good results. Bioaerosol sampling may be normal or aggressive. The primary objective of bioaerosol sampling for the average investigator is to determine the relative concentrations of biological contaminants such as mold, actinomycetes, or bacteria in problem indoor environments in the hope of determining whether levels are excessive or within acceptable limits. Conduct of measurements for either chemical or biological contaminants are a common practice in problem-building investigations.