How to (Locally) Re-Zero Total Gas Units on the Bloodhound

Because the Bloodhound operates on a relative gas presence principal, it is possible for the readings
on the device to show the presence of gas at a flat rate when there is none.  When this condition
occurs, a simple re-calibration or "re-zeroing" of the Bloodhound device is in order.

PREREQUISITES:

To determine if your Bloodhound device requires re-zeroing, identify if the following conditions
are present:

1)  Determine whether the Bloodhound actually needs to be re-zero'd:
     a)  Are you getting a relatively flat line of gas reading?  For example, yourBloodhound may
          be "zero'd" to 100 units, so the gas line would be aflat 100 units.
     b)  Pull the sample line, and check thefollowing:
          i)  Does the Gas reading go to your previously set "zeropoint"?  If yes, the bloodhound 
              probably does NOT need to bere-zeroed.
          ii)  If the Bloodhound does not go to the previous zeropoint, or goes to a flat out
              zero (0.0 units), then theBloodhound most likely needs to be re-zeroed.

2)  Someone must be present on-site with the Bloodhound to complete this tutorial.

HOW TO:

To accomplish re-zeroing gas reading for your Bloodhound Instrument, follow these steps:

1)  Remove the sample line from the sample line inlet on the Bloodhound:
      

2)  Watch the total gas reading on the bloodhound's LCD and wait for the gas to settle
     out to whatever its current "zero point" is.  This may take anywhere from a few
     seconds, to a couple of minutes or so.  Once it stabilizes, move on to the next
     step below.
    

3)  Turn the knob on the face of the Bloodhound until the menu says "Gas Unit Zero"
      

4)  Press the "Enter/Mute" button.  You are now in "Gas Unit Zeroing Mode".
     

5)  Let the reading settle for about 30 seconds or until it stabilizes.
6)  Turn the knob to the left until the reading is as close to zero as possible WITHOUT
     BEING NEGATIVE.
7)  Press the "Enter/Mute" button again.
8)  Hit the "Start/Stop" button in the upper-left to escape the current menu. 
     NOTE:  Letting any menu sit for more than 60 seconds will automatically escape.
     

Congratulations!  You have re-zeroed the gas reading for your Bloodhound Unit!