Several analyzer types are of sufficiently sound design and manufacture to meet the industry-standard requirements for general purpose gas detection. Many of these also maintain this accuracy under normal conditions for a reasonable period of time following calibration.
It is much less common, however, for the accuracy to be maintained for the following, that are routinely found in industrial processes:
An analyzer should respond uniformly to all solvents that might be used. Any differences between individual solvent response factors should not reduce the margin of safety. Typically, this means that the calibration is based upon that solvent producing the lowest response, so the analyzer indicates the true concentration of this one solvent and it indicates readings higher than actual concentration for all others in use.
In verifying the analyzer's range of response to different solvents, it’s best to obtain calibration data based on the response to solvent concentrations expressed in terms of LFL.
Do NOT use the following:
- Response factors based upon weight-percentages (such as milligram carbon per normal cubic meter), these may be deceptively close in response until they are translated into terms of %LFL
- Calibrations which are based upon calculations and have not been empirically tested and proven using actual solvent mixtures