Alco-Sensor FST Accuracy Check Procedure - Page 1

An Accuracy Check should be performed periodically. The frequency should be determined by your Quality Assurance Program.

Prior to running an Accuracy Check you should make certain that the Standard you will be using is current and all of the operating parameters for that device have been met:

  • Have as little tubing as possible between the gas out port of the standard and the mouthpiece of the Alco-Sensor FST.
  • If using a Wet Bath or Dry Gas Standard check the expiration date
  • If using a Wet Bath Standard check the temperature
  • Purge the simulator or dry gas regulator for several seconds
  • Know the current expected value of the Standard gas by using a True-Cal (II) or Elevation Chart
  • If you keep a calibration log, one should be maintained for each Alco-Sensor FST

Tools Required: Before beginning have items available: instrument, calibration standard, new mouthpiece


  • Dry Gas Standard & Regulator*
    (6 liter per minute (lpm) flow rate for automated or manual sampling)
    (1.5 liter per minute (lpm) flow rate for manual sampling)
    See the difference between the two.
  • True-Cal or True-Cal II Device
  • Alco-Sensor FST
  • New Mouthpiece


Note: A calibration standard can be a: 
  • Dry Gas Cylinder and Regulator
  • Wet Bath Simulator and Solution

For this demonstration, a dry gas cylinder is used as the standard - value (at sea level) of.082%. A True-Cal device was used to give the true value  of the standard at the time of our demonstration – the True-Cal shows   the expected gas value adjusted for    the current atmospheric pressure. Therefore, the target value for this demonstration is .081


True-Cal displays .081

Note: While wet bath Standard accuracy checks can be performed throughout the full instrument temperature range of 0ºC - 50ºC, if you are using Dry Gas as your Standard for accuracy checks, then the unit and gas should be at or between 10ºC and 40ºC.

The result of an accuracy check should not differ from the expected value by more than the tolerances prescribed by the program guidelines under which the Accuracy Check is being administered.  Usually these tolerances range from ± .005 g/210L or 5% whichever is greater, to ±.010 g/210L or ± 10% whichever is greater.