TM 10-6640-215-13 2-2.       OPERATOR CONTROLS AND INDICATORS - continued . Table 2-10.  Gum Bath System Controls and Indicators Control or Indicator Function Pyrometer Indicating    and    controlling    device    for    gum    bath    preset temperatures. Air Flow Indicator Provides  indication  of  air  flow  to  gum  bath.    Calibrated  in pounds and ounces, corresponding to flow of air in liters per second. Air Flow Regulator Regulates  air  to  gum  bath.    The  rate  of  flow  required  is  1 liter per second (     15 %). Temperature Control (Steam) Control temperature of the high pressure boiler steam output up to 5500F (228°C). AUX Switch Turns the high pressure boiler heater circuit ON or OFF. INT Switch Turns the internal heaters of the gum bath ON or OFF. GUM BATH Hood Light Switch Controls hood light operation. Fume Hood Light Switch Controls hood light operation. Fume Hood and Gum Bath Hood Controls exhaust fans operation. Exhaust Fan Switches and Indicator Lights Indicator lights are on to indicate exhaust fan operation. Boiler ON/OFF Switch Controls operation of low pressure boiler. Low Pressure Boiler Automatic Maintains low pressure boiler water level. Water Feeder System Operating Control Maintains low pressure boiler steam output to gum bath. HI Limit Control and Pressure Protects boiler from damage if boiler pressure if too high. Relief Valve Boiler Sightglass Indicates water level in low pressure boiler. 2-21