Dry Gas Methodology - Dräger Alcotest 9510 Technical Manual

8

Dry Gas Methodology

8.1 General Information
CAUTION
!
The penalty for refilling a gas cylinder, or flying on an
airplane with compressed gas, can result in a fine and/
or imprisonment. Refer to the Material Safety Data
Sheet (MSDS) for proper handling, care, storage and
disposal of dry gas cylinders.
Calibration checks are performed to validate the accuracy of
EBTs. It is recommended that the National Institute of
Standards and Technology (NIST) traceable gaseous Ethanol
standards be used and that the cylinder is approved by NHTSA
or is on the Conforming Products List (CPL).
8.2 Dry Gas Component Specifications
Dual stage regulator with a flow rate equal or greater than

3 liters per minute.
Male/Female connectors provide easy positive connection.

The gas hoses are configured with check valves to prevent

the backflow of gas.
Internal solenoids control the flow of gas.

Gas canisters are easily changed.

8.3 Using Dry Gas
In the Federal Register of August 13, 1997, Model
Specifications for Calibrating Units for Breath Alcohol Testers;
Conforming Products List of Calibrating Units (97 F.R. 43416),
NHTSA addresses two topics regarding the use of dry gas
standards: extreme cold temperatures and atmospheric
pressure.
8.3.1 Cold Temperature Exposure
Low temperature Storage
When the mixture reaches a given temperature (the dew point
of the ethanol), a small portion of the ethanol in the mixture re-
turns to the liquid state and condenses on the cylinder's inner
walls. If it is suspected that the cylinder has been exposed to
temperatures below 35 °F, the cylinder should be allowed to
warm up to room temperature (68 - 77 °F) for 24 hours before
use. As the temperature of the mix rises, condensed ethanol
will return to its original gaseous state.
8.3.2 Atmospheric Pressure
When a Calcheck is performed, some of the gas in the cylinder
is released by operating the release valve. The volume of the
released gas will expand according to the prevailing
atmospheric pressure. The gas is prepared so that the desired
concentration is obtained at sea level pressure of 760 milliliters
of mercury. However, atmospheric pressure varies slightly
from day to day and can change suddenly. The most significant
effect comes from high elevations, where prevailing
atmospheric pressure is significantly lower than 760mmHg*.
Atmospheric pressure corrections are made using an equation
derived from the Ideal Gas Law: C=C
concentration and P is the prevailing atmospheric pressure.
*Please note, 760mmHG is equivalent to 1,013 millibar.
Dräger Alcotest 9510 Washington Technical Manual V3.1 2014
8.3.3
Please refer to the gas manufacturer's Material Safety Data
Sheet.
8.4
During the breath test sequence, the 9510 will monitor the dry
gas cylinders to ensure following criteria are met: the
transducer is connected to the 9510, sufficient pressure is
available in the cylinder, and the cylinder expiration date is not
past. If the 9510 detects any of the above conditions for the
primary cylinder, it will check the secondary cylinder. If the
secondary cylinder meets the criteria, the instrument will
prompt the operator to switch to alternate drygas cylinder inlet.
If neither cylinders meet the criteria, a drygas cylinder error will
be displayed and the test sequence will be aborted.
XP/760, where C is
760
Shipping and Storage
Cylinder Pressure Monitoring
Dry Gas Methodology
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