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RESPIRATORY <br /> EXPOSURE LIMITS" <br /> COMPOUND IDLH3 PELa STEL* <br /> Benzene c 1 5 <br /> Ethylbenzene 1 2000 100 125 <br /> Toluene 2000 100 500 <br /> Xylene 1000 11 100 1 150 <br /> NOTES <br /> Units are parts-per-million (ppm) in air. <br /> Immediately Dangerous to Life and Health (published by National Institute for <br /> Occupational Safety and Health—NIOSH, June 1990). <br /> ° Carcinogen (NIOSH, June 1990). Original NIOSH IDLH = 3000. <br /> ° Permissible Exposure Limit expressed as 8-hour time weighted average (Cal <br /> R OSHA/California Code of Regulations - Title 8; June 7, 1991). <br /> Short Term Exposure Limit expressed as a 15-minute time weighted average not to <br /> be exceeded during workday (Cal OSHA(Title 8; June 7, 19911. <br /> During this undertaking, on-site respirators will consist of the half-face type fitted with <br />' organic vapor cartridges (AO-R51 HE). Respirators will be worn if photoionization <br /> detector (PID) monitoring indicates total organic vapors of 20 ppm or greater within <br /> the primary work zone breathing space for more than 10 minutes. If the total organic <br /> vapors are consistently greater than 50 ppm, full-face respirators would be worn and <br /> consideration will be given to potential engineering controls and/or upgrading personal <br /> protection. <br /> Explosion Hazard <br /> During PID air monitoring, ten percent of the Lower Explosive Limit (LEI_) for <br /> ethylbenzene would be considered the project safety standard. The LEL for <br /> ethylbenzene has been set by the National Institute for Occupational Safety and Health <br /> (NIOSH) at 1 .0 percent in air. Ten percent of 1 .0 is equivalent to 1000 ppm. <br /> Monitoring would be performed on vapors emanating from any excavation or spoil. All <br /> equipment would be shut-down while further safety alternatives are evaluated if an LEL <br /> meter indicates explosion potential and/or if PID readings indicate near 1000 ppm <br /> levels. A dry chemical fire extinguisher would be on-hand at all times during this <br /> undertaking. <br /> WORK ZONES AND SECURITY MEASURES <br /> The site is located within the fenced UPS facility. The majority of our work will be performed <br /> within the immediate area of the existing excavation. The general work area will be clearly <br /> marked to keep non-essential personnel away from any hazard. Fallowing excavation <br /> activities, the excavation will be backfilled. <br /> - 2 - <br /> â–  Geotechnical <br /> it VIII <br />