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Working on the Interior of Tanks (Tank Entry) <br /> (Tank Atmospheric Testing Levels Before and During Tank Entry) <br /> 1. Oxygen Levels % by Volume <br /> RANGE <br /> Minimum Ideal Maximum <br /> 20.0% 20.8% 21.0% <br /> 2. Flammable Vapor (Gas) (% of Lower Explosive Limit) <br /> RANGE <br /> 0 - 5% LEL <br /> If flammable vapor levels are detected up to 5% LEL, either inside the tank or from the <br /> vapors being emitted from the tank during tank venting, assess where the vapors may <br /> be coming from. Make sure the tank has been properly cleaned and is isolated from <br /> other tanks. Operate the gas indicator and the venturi continuously while inside the <br /> tank. <br /> RANGE <br /> 5.1 - 10% LEL <br /> If flammable vapor levels are detected between 5.1% - 10% LEL, either inside fhe tank <br /> or from the vapors being emitted from the tank during tank venting, exit the tank and do <br /> not enter the tank until vapor levels are below 5% LEL. Assess where the vapors may <br /> be coming from. Make sure the tank has been properly cleaned and is isolated from <br /> other tanks. Continue to vent the tank and periodically retest for vapor levels. If vapor <br /> levels do not fall below 5%, call the field service coordinator or plant manager. If tank <br /> entry is approved, wear an organic vapor cartridge respirator at all times. Operate the <br /> as indicator and the venturi continuously while inside the tank. <br /> RANGE <br /> 10% - 20% LEL <br /> If flammable vapor levels are detected between 10.1% -20% LEL, either inside the <br /> tank or from the vapors being emitted from the tank during tank venting, do not enter <br /> the tank for any reason. Continue to vent the tank and periodically retest for vapor <br /> levels. Make sure there are no potential ignition sources in the area. If vapor levels do <br /> not fall below 5%, call the field service coordinator or plant manager. <br /> Above 20% LEL <br /> If flammable vapor levels are detected above 20% LEL, either inside the tank or from <br /> the vapors being emitted from the tank during tank venting, do not enter the tank for <br /> any reason. Continue to vent the tank. Be aware of vapor levels outside the tank. <br /> Make sure there are no potential ignition sources in the area. Restrict work within the <br /> immediate area and around the tank during tank venting. Move to an area upwind of <br /> the vapors during tank venting. Periodically retest for vapor levels. If vapor levels do not <br /> fall below 5%, call the field service coordinator or plant manager.' <br /> TABLE 2 <br /> 28 <br />