Why is Gas Detector Calibration Important?
So many job sites and workplaces pose a risk of injury, illness, or death from hazards related to breathing. This can be oxygen deficiency, combustible gases or toxic gases. Gas detectors have become vital tools in a range of jobs across many industries. These portable gas monitors can, without exaggeration, be the difference between life and death for many workers. These tools exist to minimize such risks. Properly verifying the function and accuracy of gas detector meters at the start of each day's use will help to ensure that every worker finishes the job safely.
These meters, referred to by OSHA as “direct-reading portable gas monitors” or DRPGMs, serve as a frontline defense against invisible gas hazards in a workplace or public facility. They are useful in industrial and manufacturing sites, in agricultural grain sites, storage tanks, in utility facilities and even in commercial/office buildings and residential areas being inspected. Gas detectors can provide measurements, warning alerts and danger alerts.
Combustible and non-combustible gas detectors
There are several kinds of gas detectors available. Any time there is a risk of fire or explosion due to combustible gases either leaking or accumulating in hazardous amounts, combustible gas detectors can alert workers and occupants of what levels of gases are present and to exit promptly and safely. These combustible gas detectors are responsible for notifying workers to gases like Methane, Hydrogen, Propane, Ethylene, Ethane, Hexane, Benzene, Isobutane, Ethanol, Acetaldehyde, Formaldehyde, Toluene, P-Xylene, Ammonia, and Hydrogen Sulfide. Detectors are also good at finding common gas mixtures like natural gas, paint thinners, industrial solvents, dry cleaning fluids, and gasoline. Besides combustion risks, inhaling many of these gases could lead to severe sickness, permanent injuries or illness, or death.
Some gas detector meters are focused on gases that are not combustible but are equally harmful—principally, carbon monoxide or CO. Carbon monoxide is often a byproduct of a combustion source like a motor, engine, furnace, boiler, heaters, appliances, etc. It should always be vented properly out a chimney or exhaust flue. When there is a blockage, CO gases can leak into an occupied area exposing people to a deadly, invisible, scent-less gas. Having a handheld detector can offer specific insights on the amounts of CO present and whether that increases or decreases based on location, helping you trace the source.
Why calibration of gas detectors is important
The number one reason for routine calibration is Worker Safety. With accurate readings of gas concentrations, job sites can prevent worker illness, injury or death.
Over time, gas detectors may lose their accuracy. Over time, this can lead to false-negative readings or low-priority positive readings. For example, many meters over time suffer from “calibration drift” which means their reference points for alarm conditions shift and readings may not be accurate. This can happen for several reasons
- exposure to certain substances that degrade sensors
- extreme environmental factors like high/low heat and humidity
- highly polluted air with many particulates
- over exposure to gases or vapors it’s intended to detect
- rough handling of the meter affecting components’ accuracy
- harsh operating or storage conditions
- weakened batteries
OSHA recommends daily calibration, or more frequently if needed, to ensure accuracy. Many meters don’t show apparent damage. So routine testing and calibration can expose these risks. It may be a matter of replacing a sensor or the meter as a whole.
Every day: bump testing or ‘function check’
A daily bump test can be performed, following the meter manufacturer’s instructions. Generally, it involves using a “challenge gas” that’s passed over the sensor to see if it sets off the meter’s alarms with expected sensor performance. This isn’t about accuracy, but instead is focused on alarm testing.
Gas detector calibration check
After zeroing the meter, a user should expose the meter sensor to a test gas supplied in a cylinder. A test is run to see if the meter’s reading of the gas matches the concentration on the test gas cylinder label. Coming in at ± 10-20% of the test-gas concentration, the meter passes. If not, a full calibration is needed. Again, why is a gas detector calibration so important? Worker safety depends on the right tools, operating properly.
Full calibration of gas detectors
Always follow the manufacturer’s guidelines for calibration. Calibration should always be done in an environment similar to (if not the same as) the environment where detection will be performed, in terms of similar temperature, relative humidity, barometric pressure.
Operators need to have training to perform a full calibration on the field. Training should cover the use of all the calibration tools—test gas tank/cylinder, regulator, tubing, adaptor, etc. Test gases should be certified traceable and not expired—reactive gases lose stability after a period of time.
The importance of gas detector calibration
Whether you are an industrial hygienist or a home inspector, having the right tools is part of the strategy. The right tools like gas detectors and meters also need the right calibration. Lives may depend on it.