Multi-gas detectors and other detection technologies are crucial to minimizing injury and illness in the workplace. A lot of hazardous atmospheric conditions can’t be detected through human senses alone, and equipment that can test the air in a confined space can mean the difference between life and death. However, equipment alone can’t protect lives unless workers are properly trained in using and calibrating it. Calibration of gas detectors is just another part of regular equipment checks, and is integral to creating a safe workplace. The experts at PK Safety have information and advice on proper detector calibration procedures to make sure your gas readings are as accurate as possible.
Keeping instrument reference points consistent is important for worker safety. Calibration drift can happen over time because of chemical degradation of sensors and the natural drift in electronic components. Multi-gas detectors are exposed to extreme environmental conditions that can affect their performances, such as temperature, humidity, airborne particles and vapors, sensor poisons and inhibitors, and high concentrations of target gases. Add in that they might get dropped on hard surfaces or in water or handled often enough for the vibrations to affect electronic components, and your devices will need calibration to keep working effectively.
It’s best to follow the manufacturer’s guidelines for your gas detector when it comes time to calibrate it. How you calibrate your monitors depends on the work you’re doing, how many monitors need servicing, and how often they are used. Some businesses are fine manually calibrating their detectors because they don’t have hundreds of them, and some businesses use monitors seasonally and are fine with calibrating them every time the monitors are used.
There are two tests to perform to determine if monitors are working correctly, depending on your needs: a bump test and a full calibration. Conduct all tests in a clean environment with fresh air and with calibration gas certified and traceable to the National Institute of Standards and Technology (NIST).
A bump test before you use a gas monitor is highly recommended and easy to perform. Bump tests expose the gas monitor’s sensors to a target gas to test whether the alarm triggers, before you take the monitor into the field. Instruments must be zeroed before you test them, to provide more accurate results. Your monitor comes with a clip and a hose to secure over the sensor plate; attach the other end of the hose to the calibration gas and regulator, turn on the monitor and let it boot up, and open the regulator to let enough gas to trigger an alarm flow into the monitor. This should take about 10 seconds yet no more than 20 for the monitor to go into alarm. Comparing the reading on the monitor to the quantity of gas present is how you determine if the monitor is properly calibrated. If the response is within an acceptable tolerance range (the detection equipment manufacturer will provide acceptable tolerance ranges), then the calibration is verified; if not, proceed to a full calibration.
If the bump-test results aren’t acceptable, or either after the detector has been serviced or potentially severely damaged, the multi-gas detector needs to be completely calibrated. A full calibration adjusts the gas monitor’s reading so it responds to a known concentration of test gas. Some disposable monitors come with instructions stating that no calibration is required for the life of the instrument, but for safety’s sake, regular bump testing is important to make sure the device responds. The sensors in disposable monitors are the same ones used in unlimited life monitors, are just as sensitive, and are subject to the same kinds of conditions.
Making sure your data is accurate is important for legal protection as well. Multi-gas monitor readings only hold up in court as incontrovertible if the gas detector is properly calibrated before and immediately after each use to ensure it’s functioning properly. Keep a written record of calibrations for the life of each instrument so workers can identify the ones that needed excessive maintenance or are prone to inconsistent readings.
Although you should follow the manufacturer’s guidelines for calibration and bump testing when you can, they’re not always consistent between devices — despite those devices using the same sensors. Many companies develop their own testing intervals for their monitors. Companies that use their devices daily tend to calibrate every four to six months, but bump test more frequently. Our clients who use their monitors every 30 days or less usually calibrate them each time the monitors come out so they can feel confident in the devices’ responses. Test your instruments more frequently if you suspect there are conditions that could affect their performance — such as sensor poisons, damage or extreme atmospheric conditions.
Bump testing before each use of a multi-gas monitor can extend its calibration cycle up to three to six months, according to information from the president of RKI Instruments in an article for the National Safety Council. Less-frequent verification is acceptable in cases where calibration is verified daily in a 10-day period in the intended atmosphere, during which no adjustments are necessary; regardless, the intervals between testing should never exceed 30 days.
OSHA wants businesses to have gas detectors calibrated before each use. The International Safety Equipment Association (ISEA) recommends verifying sensors are responding to test gases accurately before each day’s use by bump testing. Device calibration should be done at the locations where the equipment is going to be used and in similar conditions, if possible, to ensure the readings are accurate at the actual field location.
Do you need more gas detectors? Did you realize while calibrating your old ones that you might need to replace them? PK Safety has been in the safety business for 70 years and knows a thing or two about gas monitors, and we’re having a sale to celebrate their importance to safety. If you need answers to your worksite, safety or equipment questions, talk to one of our safety experts by calling 800.829.9580, or get in touch online.