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Alco-Sensor IV Accuracy Check Procedure

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 IV.
  • Check Expiration Date (on Wet Bath Simulator Solution or Dry Gas Tank)
  • Check Temperature of the standard (Check Wet Bath Simulator Temperature)
  • Purge the simulator or dry gas regulator for several seconds
  • Know the current expected value of the Standard gas
  • If you keep a calibration log, it should be present

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

Alco-Sensor IV Accuracy Check Procedure Part 1
  • Dry Gas Standard & Regulator
  • True-Cal or True Cal II Device
  • Alco-Sensor IV
  • New Mouthpiece
  • Calibration Tool


    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 will adjust the expected gas value for the current atmospheric pressure. Therefore, the target value for this demonstration is .080.


Alco-Sensor IV Accuracy Check Procedure Part 2
1)  Insert a clean mouthpiece into the Alco-Sensor IV. After the Alco-Sensor IV displays the temperature and the blank test result, the unit will display “Test” or “CHEK”.

(Alco-Sensor IV with Memory instruments and some ASIV/RBTIV instruments can be put into a mode where “CHEK” is displayed. This feature allows the user to identify a record on the printout and memory and as an accuracy check. It is not necessary to put the instrument in the “CHEK” mode to perform the accuracy check function. This feature is purely cosmetic and helpful to those who are concerned with record keeping. See your operators manual for instructions)

Temperature displayed



2)  Once “Test” or “CHEK” is displayed, introduce the gas sample from the standard through the mouthpiece of the Alco Sensor IV for a total of six (6) seconds.  On the fourth (4th) or fifth (5th) second press the MANUAL button on the Alco Sensor IV. The Alco-Sensor IV should make a “click” sound. Make certain that the gas sample is still flowing for at least one second after the MANUAL button is pressed.
3)  Flashing arrows indicate the Alco-Sensor IV is analyzing the sample of gas.  A result will be displayed. Flashing arrows < >


4)  Observe the three-digit reading. Displayed result – .080


Alco-Sensor IV Accuracy Check Procedure Part 3
5) Compare the displayed result to the current expected value of the standard

Note: If the result of the accuracy check is not within an acceptable tolerance (see your program QAP) from the expected value of the standard, you will need to perform a calibration followed by a post-calibration accuracy check. 

Expected value of standard used for this demonstration


6)  When “Set” displays, press the SET button on the Alco Sensor IV.7) After the SET button is pressed, an audible beep is heard.
Set button depressed


7)  Press the RECALL button to recall the accuracy check result and record the result in the Calibration Log. A result within the acceptable tolerance range implies the instrument is “in calibration”.
Recall button depressed


8) Eject the mouthpiece using the
red mouthpiece eject button after the result has been recorded.

Mouthpiece EJECT button


To demonstrate compliance with your program’s QAP it is best to keep a record or a Calibration Log for each device used for testing.  The log should contain the results of all accuracy checks and calibrations for each instrument.  This log may become a crucial piece of evidence should your test results be challenged.  The log may include information such as:

  • Date
  • Time
  • Procedure performed (Accuracy Check or Calibration)
  • Name of Technician performing procedure
  • Location
  • Identification of the Standard including Lot Number of the Standard
  • Expected Value of the Standard
  • Result of the Accuracy Check or Calibration

For more information about procedures for your Intoximeters instrument, please refer to your

  • Operator’s Manual
  • or email Intoximeters Tech Support
  • or phone the Technical Support Department at 314-429-4000
  • Or visit our Instrument Maintenance Page to view calibration information and more

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