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Challenge testing your gas detector

Challenge testing your gas detector 

Many workers will operate machinery without much thought as to how and why it works or in some cases as to whether it is actually working properly at all.

So the question is, how do you know whether your gas detector is functioning correctly?

Answer - the only true way to confirm that a gas detector is functioning and is capable of responding to gas is to expose the gas detector to a concentration of target gas that is high enough to initiate an alarm situation.

This process is often called a 'Bump Test' or 'Challenge Test' 

Worplace environments can be harsh on your gas detector and subject it to extreme shock such as being dropped from heights, run over by heavy vehicles, exposed to high temperatures, humidity, water, mud, dust, chemicals and toxic gases. As a service facility we have seen many gas detectors that have been exposed to environmental or human interference, including accidental / deliberate damage caused by piercing the sensors, destroying the audiable alarm piezo and breaking the casing seal to name a few. You have to ask yourself do you really want to put your life into the hands of a gas detector that may not be functioning properly? 
 

What should a challenge test consist of?

  • expose the gas detector to a known concentration of gas to ensure that the instrument responds
  • when the instrument is exposed to gas make sure both the audible and visual alarms activate

Who is responsible for bump/challenge testing your gas detector?

Section 9.2.1 Inspection and field-check (response check) of AS/NZS 60079.29.2:2008 Gas Detectors - Selection, use and maintenance recommends "that this is done by personnel actually operating the apparatus and is strongly recommended that it is performed before each day of use" while AS2865-2009: Australian Confined Space Standard section 3.4.50 states that "Gas monitors used for the purpose of atmospheric monitoring within a confined space should be maintained and used in accordance with manufacturer's instructions and warnings and in reference to AS/AZS 60079".

What do I need to perform a bump/challenge test my instrument?

A standard bump test / calibration kit will consist of:

  1. Calibration gas [suitable for the gas detector ie: a standard 4 gas unit will require O2/LEL/H2S/CO. Note: make sure that the gas is suited to the gas detector settings or you will not get accurate readings when bump/challenge testing or calibrating your instrument.]
  2. Regulator [as described in he manufacturer's user manual eg: 0.5LPM]
  3. Calibration cap [supplied with instrument at time of purchase]
  4. Hosing [supplied with instrument at time of purchase]
  5. Case for storage and transport

Many companies have utilised a automated test station such as the MicroDock II Calibration Dock option for their BW Technologies gas detectors. This easy to use system will allow you to challenge test your unit as well as calibration and charging.

How will you know if you instrument has failed the bump/challenge test?

  • the sensor readings will be outside of the manufacturer's allowable range
  • the audible alarm will be very soft and hard to hear
  • the visual alarms are not working

What do I do if my instrument fails the bump/challenge test?

  • the sensor readings are outside of the manufacturer's allowable range - calibrate the instrument or repair
  • the audible alarm will be very soft and hard to hear - return the instrument to your servcie agent for service and/or repair
  • the visual alarms are not working return the instrument to your servcie agent for service and/or repair

What else to consider when you are challenge testing your gas detector

  • check that the sensor filters are not blocked with dirt, mud, chemicals or any other foreign substance that may impede the sensors from detecting toxic gasis in the atmosphere, if your sensors are dirty or damaged they will need to be replaced return the instrument to your servcie agent for service and/or repair
  • check the external housing for any missing screws, cracks in the housing or any other damage that may interfere with the correct operation of the instrument, if any screws are missing or there are cracks in the housing this may allow water into your instrument thus rendering it  unsuitable for use as it may not operate to it's full functionality return the instrument to your servcie agent for service and/or repair

Some examples of damage to gas detectors that will prevent it from functioning correctly.

Challenge Test Gas Detector Water DamageWater Damage

Challenge Test Gas Detector Punctured SensorFilterPunctured Filter and CO Sensor

Challenge Test Gas Detector Damaged H2SDamaged H2S sensor 

 
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