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Confidence indicator vs. compliance indicator

June 1, 2012

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What’s the difference between a confidence flash and visual compliance indicator? My gas monitors have a button or light that flashes or beeps – what does this mean?


Responding is Andrew Saunders, applications and training specialist, BW Technologies by Honeywell, Calgary, Alberta, and Honeywell Analytics, Lincolnshire, IL.

Traditionally, portable gas monitors have an optional confidence beep, flashing LED or both to indicate the monitor is operational. This feature can be turned on or off as needed, and is not necessarily tied to monitor performance or compliance to company requirements such as daily bump testing.

Compliance indicators validate that the monitor has been bump-tested and calibrated within the required intervals set by company policy. They may even be tied to sensor condition by electronically checking sensors to confirm they are working properly.

To ensure a gas monitor will perform as intended, most manufacturers of portable gas monitors and regulatory agencies agree that a bump, or functional, test should be carried out on the instrument prior to each day’s use. Manufacturers offer confined space entry kits that provide all the equipment necessary for this operation, and docking stations can bump-test and calibrate, as well as record, the events.

A manual compliance check can take approximately three minutes per detector. Twenty detectors in an area could take close to an hour to inspect. A safety manager can quickly scan the area while auditing other safety personal protective equipment and, within a few minutes, cover the entire area. This results in saved time and money.

Sensor technologies used in today’s gas monitors have improved significantly over the last decade. Advances such as electrochemical over solid state, enhanced poison resistance, and less cross-interference have resulted in more reliable performance. This evolution is one reason why calibration intervals have lengthened.

Still, gas monitors must operate in harsh conditions and are not impervious to damage. Along with physical shock to the instrument, sensors can be damaged by gas concentrations that exceed the detectable limit. Filters and sensor ports can become obstructed by liquid, dirt and dust, producing no change in readings even though the atmospheric conditions may have fluctuated. Proper bump testing and verification of accuracy between calibrations can prevent a false sense of security.

In 2004, OSHA posted a statement, Verification of Calibration for Direct-Reading Portable Gas Monitors on its website as a Safety and Health Information Bulletin. OSHA stipulates that this is not a regulation and creates no legal obligations, but is intended to assist employers in providing a safe and healthful workplace.

Portable gas monitors are designed to protect workers against potentially life-threatening occupational environments. Verifying the proper performance is an essential part of any gas monitoring safety program. Following this protocol will ensure confidence in workers and everyone responsible for keeping them safe.

Editor’s Note: This article represents the independent views of the author and should not be construed as National Safety Council endorsements.

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