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Study Notes: AAS Safety

AAS equipment has inherent hazards associated with its use that the operator must be aware of before using the equipment. In this Study Note we will assume that the operator is competent in the use of the AAS and has a good knowledge of general laboratory safety and OHS principles. The following points outline several important aspects of AAS Safety:

  1. Exhaust System
    AAS flames produce large amounts of heat and the resultant fumes and vapours may be toxic. An efficient exhaust system is required to remove the heat, fumes and vapours. The exhaust fan must be switched on prior to lighting the flame or running the furnace. The operator should also be aware that many parts of the AAS will be hot and should be very careful when performing routine maintenance.

  2. Gas Cylinders
    Gas cylinders be located outside of the laboratory in a cool well-ventilated area. They should be stored vertically and firmly attached to the wall to avoid falling over. Piping to the laboratory should be permanent and colour coded for each gas and should include shut off valves for each supply line. The shut off valves should be within easy each of the AAS. The gas supply system should be leak tested at regular intervals.

  3. Gas Hose and Connections
    Connection of the AAS to the permanent gas supply lines is via short pieces of tubing attached to the AAS and supplied by the manufacturer. Position these hoses so that they cannot be damaged or stepped on. Ensure that only approved fittings are used to connect the hoses. These hoses and connections should be regularly inspected.

  4. Acetylene
    Acetylene iIs a flammable and sometimes forms explosive acetylides. The following rules should be observed for its use:
    • never use copper tubing for acetylene or brass with >65% copper
    • do not run acetylene at >105 kPa (15 psi)
    • never let acetylene come into direct contact with copper, silver, mercury, chlorine gas or grease.

  5. Nitrous Oxide
    This is an asphyxiant, can cause spontaneous combustion of oil and causes sufficient cooling when removed from the supply cylinder to cause freezing of the regulator.
    Leak test at regular intervals and use a heated regulator.

  6. Flammable Solvents
    Many flammable solvents may be used in AAS and the combination of flame and solvent is a hazardous situation. Always use a solvent with the highest flashpoint consistent with the analysis being conducted. Use covered containers and the smallest practical volume.

    Do not accumulate waste solvent from the spray chamber and use a waste vessel located in an open well-ventilated area and empty it often. The waste vessel should not be of glass.

  7. Burners
    Remember that the air-acetylene burner can only be use for air-acetylene whilst a nitrous oxide-acetylene burner can be used for both. Never use oxygen as the oxidant. Keep burners clear and do not allow them to block.

    Never leave a flame unattended. Turn flame off prior to cleaning the burner. Watch out – it may be hot! Use protective gloves.

  8. Liquid Trap
    This must be filled to the correct level prior to analysis.

  9. UV Radiation
    Hazardous UV radiation is emitted by flames, hollow cathode lamps, electrodeless discharge lamps, deuterium lamps and analytical furnaces. Never look directly at any of these. Operate the AAS with the door or flame shield closed and wear appropriate safety glasses.

  10. Heat Hazards
    There are many hot surface hazards for the unwary operator. Keep door or flame shield closed, use protective gloves and always turn off the flame before making adjustments.

  11. Safety Check
    Always follow approved SOPs, manufacturer’s instructions and workplace procedures prior to use of the AAS.

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