Benzene is a confirmed human carcinogen and employee exposure is a global problem. Since benzene is carcinogenic, there is no safe limit for exposure and all practical means must be tried to limit the employee exposures to lowest possible level. This paper describes the quantitative techniques used and engineering solution based approach adopted to tackle a specific benzene exposure scenario.
Complaints of VOC (containing Benzene) smell were repeatedly reported from a specific work area near the Effluent Treatment Plant (ETP) through company's online system designed for reporting and tracking of any unsafe conditions/act or incident.
Initial area surveys and investigations identified presence of slop oil in ETP plant's equalization tank as the source of nuisance.
Spot monitoring was conducted to quantify area benzene levels, using a portable monitor. Area TWA and personal monitoring was also performed to assess employee exposures. Area TWA and Personal monitoring involved active sampling using portable pumps and solid adsorbent tubes followed by Gas Chromatographic (GC) analysis. Slop oil analysis was done for identifying VOC constituents and their relative proportions.
Monitoring results indicated presence of benzene near a specific building area depending upon the wind direction. It also confirmed that overall employee benzene exposure levels were much lower than the Occupational Exposure Limit.
To improve the conditions for building inmates, a HVAC management protocol was developed as an immediate protective measure, defining specific actions based on spot monitoring results and wind direction.
Affected building required permanent protection through additional engineering controls. A project is developed to modify and upgrade existing HVAC system of the building incorporating VOC filtration system with detectors for automatic HVAC controls. Slop oil analysis data on VOC constituents was used to calculate expected VOC load for this design and for VOC filter material selection.