What’s the difference between a bump test, a calibration check, and a full calibration?
If your workers work around any gas hazards, they should be equipped with direct-reading portable gas monitors (DRPGM). These devices can be life-saving, but only if they're well calibrated and accurate. It's crucial that you train workers to know which equipment checks to perform and how often to perform them. This ensures the optimal functioning of their equipment.
A bump test (also known as a function check) involves passing a challenge gas over the DRPGM sensor(s) at a concentration and exposure time sufficient to set off the alarm. Bump tests don't measure the instrument's accuracy. They measure its ability to recognize and respond when a hazard is present.
The International Safety Equipment Association recommends conducing bump tests each day before using the equipment.
A calibration check exposes the instrument to a test gas to verify that the sensor(s) and alarms respond within the manufacturer's acceptable limits. OSHA recommends that operators check with the instrument's manufacturer for the acceptable tolerance ranges.
If the calibration check results are not within the acceptable range of + or - 10%, the operator should reset the instrument by performing a full calibration.
A full calibration adjusts the instrument's reading to coincide with a known concentration of test gas. The test gas used for calibration should always be within the expiration date and certified using a standard from the National Institute of Standards and Technology (NIST).
Regular calibration check times can vary, depending on the type of equipment used. Checks should be made according to the manufacturer's instructions, internal company policy, and appropriate regulatory agency guidelines. Employers should keep calibration records for the life of each instrument.
Keep in mind that the responsiveness of DRPGM sensors will vary with workplace environmental conditions, such as temperature and humidity. Operators should calibrate sensors in environmental conditions that are the same as (or as similar as possible to) the actual workplace conditions.
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