With most installations, the only variable that can be changed is the location of the transmitter.
In some cases, you may find that a target gas source is too close to the transmitter. Consider
other mounting locations for the transmitter or move the gas source farther away.
Maintenance
Testing the Response to the Target Gas
Carbon Monoxide or Nitrogen Dioxide Transmitters
Testing these transmitters requires that the target gas be applied to the sensor using one of
two methods. Gas can be applied from a tank of air containing a known concentration of the
target gas or from the exhaust of an operating engine to produce a level of target gas sufficient
to activate the control system. For the latter method, use a gasoline or petrol engine to
produce CO and a diesel engine to produce NO
2
.
Of the two methods of obtaining test gas, the simplest is operating an engine in the vicinity of
the transmitter under test. The engine should be placed about 10 feet away from the
transmitter so that exhaust gases will not contact the transmitter directly.
The engine should be allowed to operate until a level of the target gas is sufficient to activate
the ventilation system. Depending upon the volume of the area where the transmitter is
located, this may take from 10 to 30 minutes.
Using test gas applied from a tank has the advantage of speed as well as assurance that the
transmitter is responding accurately to the target gas. However, the gas must be applied
directly to the sensor if the response is to be close to the value present in the tank. The test
gas cannot be allowed to become diluted by the air in the room before it comes in contact with
the sensor. This reduces the concentration to a level too low to give the desired result.
IOM02
Rev 1.0 – December 22, 2020
20
CAUTION
Allowing the transmitter to come in direct contact with undiluted exhaust gases will decrease
the expected useful lifetime of the sensor. The high concentration of acids and other
components in the exhaust gas will overload the activated carbon filter inside the sensor and
will increase the effects of interfering gases on the accuracy of the sensor.
If the sensor becomes damaged, it must be replaced with a new sensor calibrated at the
factory.
