Industrial gas monitors are the silent guardians of countless workplaces, continuously sampling the air to detect dangerous levels of toxic or combustible gases. When these instruments fail, the consequences can be catastrophic, leading to injuries, fatalities, or significant property damage. One of the most critical failures is a gas monitor that won't calibrate correctly, leading to false or inaccurate data that jeopardizes safety.
Understanding the causes of calibration errors and implementing best practices are essential steps in maintaining a safe environment.
A gas monitor's calibration confirms that the sensor is accurately measuring gas concentrations. If the monitor rejects the calibration, it’s a critical sign that something is wrong. Here are the most common culprits:
Calibration gas provides the known standard against which the monitor's sensors are adjusted.
Expired Gas: Over time, the concentration of gas in the cylinder can degrade or become unstable, especially for reactive gases like H2S (hydrogen sulfide) or CL2 (chlorine). Using an expired gas mixture means calibrating the monitor against a false standard, leading to inaccurate readings.
Incorrect Gas: Using the wrong gas concentration (e.g., 50 ppm CO when the monitor expects 100 ppm) or the wrong gas type entirely will result in a failed calibration. Always match the gas type and concentration to the monitor's specifications.
Gas sensors, particularly electrochemical sensors used for toxic gases and catalytic bead sensors for combustible gases, have a finite operational life.
End-of-Life: Sensors nearing the end of their lifespan will often become less responsive, drift excessively, or fail to hold a calibration. They simply can no longer reliably detect or measure the target gas.
Poisoning or Inhibition: Certain substances, such as silicone vapors, heavy hydrocarbons, or high concentrations of H2S, can "poison" or inhibit the sensor's active material, leading to permanent damage and calibration failure.
The environment in which calibration is performed can significantly impact the process.
Temperature and Humidity: Gas monitors are typically calibrated at a specific temperature and humidity range. Extreme deviations (e.g., calibrating in a very cold or humid environment) can affect the sensor's electronic response, causing the calibration to fail. Always allow monitors to acclimatize to the calibration environment.
Pressure: While less common, significant changes in atmospheric pressure can influence some sensor types, requiring adjustment or compensation during calibration.
Preventing calibration errors requires a proactive, systematic approach embedded in a robust maintenance program.
| Cause | Best Practice / Solution |
| Expired/Incorrect Gas | Check Expiration Dates: Visually inspect all calibration gas cylinders and discard any that are past their expiration date. Verify Specifications: Always match the cylinder's gas type and concentration to the monitor's required values. Store cylinders correctly to avoid degradation. |
| Sensor Degradation | Monitor Sensor Health: Most modern monitors provide a sensor life indication. Follow the manufacturer's recommended replacement schedule (e.g., every 2-3 years) even if the sensor appears operational. Replace any sensor that repeatedly fails calibration. |
| Environmental Factors | Acclimatization: Calibrate monitors in an environment that is within the monitor's specified operational range for temperature and humidity. Allow stabilization before calibration, especially when moving a monitor from a cold outdoors to a warm indoor area. |
| General Failure | Use Factory Equipment: Utilize the manufacturer's recommended flow regulators and tubing, as incorrect flow rates can prevent proper sensor exposure. Bump Test Regularly: Perform a quick "bump test" (exposure to gas without full adjustment) before each use to verify the monitor alarms and the sensor responds. |
The use and maintenance of industrial gas monitors are not merely best practices; they are often regulatory requirements mandated by organizations like the Occupational Safety and Health Administration (OSHA) in the U.S.
While OSHA does not explicitly set a mandatory frequency for calibration for all gases, its standards and numerous interpretations emphasize the need to follow manufacturer instructions and maintain accurate monitoring for compliance.
29 CFR 1910.146 (Permit-Required Confined Spaces): This standard requires atmospheric testing with calibrated instruments before entry and often continuous monitoring during work. The accuracy of the monitor is paramount.
29 CFR 1910.120 (Hazardous Waste Operations and Emergency Response - HAZWOPER): Requires the use of appropriate air monitoring instruments and specifies they must be calibrated and maintained.
OSHA Interpretation Letters frequently stress that "calibration is necessary to ensure the accuracy of direct reading instruments."
Industry consensus standards, such as those published by the International Organization for Standardization (ISO) or American National Standards Institute (ANSI), often reinforce the need for periodic sensor verification (bump testing) and full instrument calibration to maintain safety certification.
In essence, any standard requiring the use of gas detection instruments implicitly requires that those instruments are accurately calibrated to protect workers from exposure to hazardous atmospheres.
A failed calibration is a warning, not just an inconvenience. Ignoring this sign and continuing to use a faulty monitor is a direct threat to worker safety. By treating calibration as an essential safety procedure—not a maintenance burden—and diligently addressing the causes of calibration failure, facilities can ensure their gas monitors remain reliable, accurate, and ready to protect lives. Always remember: A monitor that won't calibrate is a monitor that can't be trusted.
goSafe offers a wide variety of Instrumentation suitable for every task related to gas detection. goSafe also offers and Instrumentation Management program. We can help keep your monitors working properly with warranty, repair, calibration, and recertification services. We'll even handle inventory and shipping. Contact Us for more information or for any questions related to safety and safety-related products.
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