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7.7.2.2. Establish how you will communicate with the attendant (if there is an emergency and you can't self-rescue) while you are inside the tank. Note that with the venturi running, it may be difficult to hear. 7.8. Before Tank Entry 7.8.1. Site Supervisor Responsibilities 7.8.1.1. Contact the customer to determine the last product inside the tank. Request a copy of the Material Safety data Sheet (MSDS). 7.8.1.2. Review the MSDS for toxic substances. 7.8.1.3. If the tank has contained leaded gasoline, lead additives or lead products, the tank must be cleaned and documented that it is lead-free if the walls of the tank will need to be disturbed (such as from cutting, grinding, sanding). Before conducting work that may introduce lead into the air, call the corporate engineering services department in Minneapolis at 952-887-1890 for guidance before proceeding. Note: The federal government started to reduce lead in gasoline in 1974 under the authority of the Clean Air Act Amendments of 1970. By the early 1980s, gasoline lead levels had declined about 80%. Beginning in January of 1986. the allowable content of lead was reduced to 0.1 grams per leaded gallon (gplg). Lead was banned as a fuel additive in the United States beginning in 1996. (Source: Newell and Rogers, Nov. 2003, "The Market-based Lead Phasedown.") 7.8.1.4. Make sure the tank has been vented with a venturi running for at least 30 minutes. 7.8.1.5. Perform a function check of the calibrated combustible-gas indicator. 7.8.1.6. Conduct initial testing from outside the tank to determine maximum atmospheric concentrations before tank entry. 7.8.1.7. Test the exhaust air for flammable vapor levels. 7.8.1.8. Refer to Table 2 for acceptable atmospheric levels for tank entry. 7.8.1.9. Shut off the venturi for at least 15 minutes to allow the tank to reach equilibrium. 7.8.1.10. Since hydrocarbon vapors are heavier than air, take measurements through an access opening at various levels (at least every four feet) and as close as possible to the bottom of the tank. Specific locations to sample are included in Appendix E. Note: The sampling hose must be long enough to reach the bottom of the tank. Do not allow fluids to enter the pump or testing instrument. The hose should be clear 25