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Do gas monitors fail?
Gas monitors, like every piece of electrical equipment, develop faults and fail to work properly from time to time. Although designed to notify you when an electrical fault occurs, they are often unable to tell you if the gas sensing cells have drifted, a sounder no longer works or a visual indicator, such as a light have failed.
So how can you tell if your multigas monitor (confined space atmosphere monitor) is working properly?
How can you identify if the sensors have drifted away from their calibration?
Have the sensor openings become obstructed with mud?
Did dropping the gas monitor break something inside?
All of these questions need to be answered every time you use your gas monitor, this is a life critical piece of equipment and chancing that it is working is not an option!
So what do I need to do?
For any gas detector used in confined spaces it is stated under Paragraph 184 of the Confined Spaces Regulations 1997, that the manufacturer’s recommendations on calibration and testing intervals must be followed. Bump checks are almost always recommended by every manufacturer as part of a daily check, and as such these checks become mandatory and should be undertaken before use.
Are these bump checks really necessary or is it just a money making ploy?
I am often asked “are these checks really necessary, or is it just a money making ploy by manufacturers of the equipment”. Now, I can understand why people ask this question, as all the expenses add up, but let me ask you this “How do you know that gas detector is working properly?” and the simple answer is “you don’t!”. It’s easy to become complacent when using gas monitors, but we must always remember why we are using them; to guard against the potential for instantaneous gaseous threats to our life and health. I think this alone is enough that you should ensure that your gas monitor is working correctly every time you use it!
So what causes my multigas monitor to drift and not function properly?
We stress the need to verify accuracy on a regular basis for a number of reasons!
To guard against any loss of sensitivity due to sensor poisons or suppressors possibly present in the atmosphere being monitored; due to aging, coating or desiccation of the sensors; mechanical damage due to dropping or immersion; or other causes.
In the case of combustible gas sensors, damaging effects can be caused by high concentrations of gas or exposure to sulfides, halogenated compounds, tetra-ethyl-lead, or silicone-containing lubricants. For PIDs, exposure to heavy, oily compounds or some phosphorus compounds can coat the lamp and sensor, and water condensation can etch the salt crystal lamp window.
Other factors can also cause loss of apparent sensitivity, such as leaks in the probes, connecting tubing or pump, and improper calibration or correction factors.
So what is a bump check and how often should I perform it?
A functional (bump) test is a means of verifying calibration by using a known concentration of test gas to demonstrate that an instrument’s response to the test gas is within acceptable limits, the alarms respond to the gas within the manufacturer’s acceptable limits. This is typically ±10% to ±20% of the test gas concentration applied unless otherwise specified by the manufacturer.
You must perform a bump test in the following circumstances:
A functional (bump) test or full calibration of direct reading portable gas monitors should be made before each day’s use in accordance with the manufacturer’s instructions using an appropriate test gas.
Any instrument which fails a functional (bump) test must be adjusted by means of a full calibration procedure before further use.
If environmental conditions which could affect instrument performance are suspected to be present, such as sensor poisons, then verification of calibration should be made on a more frequent basis.
So what do I do now?
Bump testing a gas monitor is incredibly easy and takes 30 seconds of your day. As such, I would recommend looking into introducing bump checking policies and procedures for all your gas detection equipment. Bump checks can be undertaken manually using a calibration gas canister and the appropriate calibration cap for your gas monitor, or can be automated through the use of calibration stations. With Honeywell/Rae systems gas detection equipment, bump and calibration stations are available for all equipment and range typically from £500 to £1500.
If you would like to arrange for us to talk to you with regard to your current calibration and bump testing facilities or would like to arrange of your equipment please contact us at firstname.lastname@example.org/calibration or +44(0)1904 373 018