 Exposure assessments in occupational settings are most often performed by occupational/industrial hygiene (OH/IH) professionals who gather "basic characterization" consisting of all relevant information and data related to workers, agents of concern, materials, equipment and available exposure controls.The exposure assessment is initiated by selecting the appropriate exposure limit averaging time and "decision statistic" for the agent.Typically the statistic for deciding acceptable exposure is chosen to be the majority (90%, 95% or 99%) of all exposures to be below the selected occupational exposure limit.