Contractors have complained for years about the expense in both downtime and money of sending their combustion analyzers to the factory for calibration. This is what most manufacturers recommend and is the best way for them to address liability or accuracy issues. I’ve found that most manufacturers have little to no field experience when it comes to using these instruments.
So, they take a safe rather than sorry approach. But is this annual combustion analyzer calibration really necessary? What about those CO alarms that people install in their homes? Most have a five-year warranty and are never required to be calibrated. That might be another story for the future.
So why would I, one of the most vocal people about CO poisoning, question calibration? Sometimes I feel like I’m the only one in the park on the teeter-totter.
Why Calibrate?
Manufacturers first began requiring analyzer calibration in 1985. The main reason: these early portable combustion analyzers were the first to measure carbon monoxide (CO) using electro-chemical sensors.
Other than the CO accuracy, the only other sensor that needed calibration was the O2 sensor and it self-calibrated every time an analyzer was turned on. The temperature probe, which is not as critical, could be checked in boiling water.
So, here’s some questions to think about: Does the calibration or accuracy of the CO sensor have an effect on detecting CO problems? How accurate were the chemical CO tubes that were used for years?
Unlike today’s digital CO meters, the chemical glass tubes only measured CO above 100 ppm and each tube cost $3.00. Anyone claiming to have years of experience using these glass tubes is no different than someone who studied time using a sundial.
However, even the sensitivity of the tubes did not lead to misdiagnosis. I want to discuss what really causes inaccuracy in detecting or diagnosing CO problems, but first a little history, based on 40 years of field experience.
Some Background
As a salesman and demonstrator of the first portable digital combustion analyzer with a carbon monoxide sensor, I had to ensure that instrument was accurate. Again, as mentioned above, the manufacturer recommended the analyzer be sent back to the factory for calibration. This certainly was an inconvenience because doing that would leave me without a demo unit to show potential customers.
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