After scouring the internet for the best technical explanation, we landed on Wikipedia for a great definition. Following their definition is the Cal Gas Warehouse definition in laymen’s terms.
Wikipedia defines Calibration Gas as follows:
“A calibration gas (also referred to as cal gas and calgas) is a reference gas or gas mixture used as a comparative standard in the calibration of analytical instruments, like gas analyzers or gas detectors, Therefore, a calibration gas has to be a precisely defined nature of composition, like zero gas or span gas; for example 50 ppm Carbon Monoxide in Nitrogen.
To be a calibration gas, that gas must be traceable to a national (NIST) or international standard. Traceability is the unbroken chain of comparisons to an acceptable international standard. The calibration gas standard establishes a known analyzer response to a certified chemical component concentration. In the calibration preparation tolerance (PT) and certification/analytical accuracy (CA) are of utmost importance.
Preparation Tolerance (PT) is the concentration range that includes minor component and concentration. PT is actually measured in range of concentration. For instance, a cal gas of 50 ppm CO and balance Nitrogen having PT +/- 10% contains between 450 ppm and 550 ppm. PT can be minimized by using latest technologies is decided on the basis of the manufacturing such gases. Preparation tolerance is decided on the manufacturer’s experience and the customer’s requirement.
Certification/analytical accuracy (CA) is defined as the agreement of measured values with its true value. Certification values are determined statistically, considering the uncertainties accompanied by the international standard (reference standard) to which it is traceable, instrument uncertainty and the instability (reactivity) of the gas in the container.
Cal Gas Warehouse laymen’s terms on Calibration Gas
A calibration gas is a defined concentration/mixture of gases that are used to calibrate to an acceptable defined range (span) within a gas detector. ALWAYS check with the manufacturer for the exact concentration your gas detector requires. NEVER use expired gas and check with your safety director or supervisor if there is any uncertainty or hesitancy on what your required cal gas(es) might be. Please refer to our commonly used gas detection terms, if you are unsure of terms or abbreviations.
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