Gas Detector Types and Operation

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Questions and Answers

What term refers to the sensor's reaction to an interfering gas?

  • Response Time
  • Cross Sensitivity (correct)
  • Noise/Drift
  • Dynamic Range

Which factor describes the ability of a sensor to react to its specific gas in a specified time frame?

  • Precision
  • Limit of Detection (LOD)
  • Response Time (correct)
  • Accuracy

What does 'Limit of Detection (LOD)' represent in gas detection equipment?

  • The accuracy in measurement
  • The precision of measurement under unchanged conditions
  • The ability to withstand electromagnetic fields
  • The lowest quantity the instrument can detect with confidence (correct)

Which term represents the degree to which repeated measurements under unchanged conditions show consistent results?

<p>Precision (D)</p> Signup and view all the answers

What does 'Dynamic Range' measure in gas detection equipment?

<p>Ratio between the largest and smallest possible signals (B)</p> Signup and view all the answers

Which factor defines how much readings fluctuate when the concentration of a substance remains constant?

<p>Noise/Drift (B)</p> Signup and view all the answers

What is the purpose of Intrinsic Safety in gas detection?

<p>To limit energy levels above the required threshold for igniting hazardous atmospheric mixtures (D)</p> Signup and view all the answers

Which category of hazardous atmospheres includes oxygen deficiency and asphyxiating gases?

<p>Oxygen deficiency/Asphyxiating gases (D)</p> Signup and view all the answers

What type of instruments are commonly used in mine rescue gas detection?

<p>Direct-reading instruments (B)</p> Signup and view all the answers

Why is it important to select gas detection equipment tailored to the specific incident's needs?

<p>To facilitate rapid decision-making based on real-time sampling information (B)</p> Signup and view all the answers

What is the primary purpose of direct-reading instruments in gas detection?

<p>To provide information after sampling (D)</p> Signup and view all the answers

What should be considered before conducting any gas testing?

<p>The presence of intrinsically safe personal protective equipment (A)</p> Signup and view all the answers

What is a key advantage of multi-gas detectors?

<p>They use separate sensors for different gases (D)</p> Signup and view all the answers

What is a limitation of using multi-gas detectors?

<p>Their sensor sensitivity degrades over time (D)</p> Signup and view all the answers

How can a multi-gas detector be more versatile in its usage?

<p>By having an internal motorized pump (C)</p> Signup and view all the answers

What is a characteristic of oxygen sensors in terms of lifespan?

<p>1-5 years (D)</p> Signup and view all the answers

Which type of gas sensor has the longest lifespan according to the provided information?

<p>Infrared gas sensors (A)</p> Signup and view all the answers

What is the responsibility of the operator when performing sample tests for gas detection?

<p>Following all manufacturer's specifications and guidelines (A)</p> Signup and view all the answers

What is the purpose of the colorimetric (tube-style) gas detectors mentioned in the text?

<p>To draw a known volume of air through a detector tube designed to measure the concentration of gases and vapors (C)</p> Signup and view all the answers

What should be done before using a colorimetric tube-style gas detector?

<p>Refer to the manufacturer's instructions and perform a pump leak test (B)</p> Signup and view all the answers

How are the readings from colorimetric tubes typically read?

<p>By comparing the color change to a scale printed on the tube (C)</p> Signup and view all the answers

What consideration is important when using short-term indicator tubes?

<p>Comparing the readings to appropriate short-term exposure limits (A)</p> Signup and view all the answers

What is one of the advantages of colorimetric (tube-style) gas detectors mentioned in the text?

<p>Operates with one hand and does not need batteries (A)</p> Signup and view all the answers

Why is it important to store colorimetric tubes properly?

<p>To avoid exposure to excessively low or high temperatures and direct sunlight (C)</p> Signup and view all the answers

What is a major limitation of gas tube testers mentioned in the text?

<p>They have a limited shelf-life (D)</p> Signup and view all the answers

Which of the following is a characteristic of electronic gas detectors as described in the text?

<p>They use plastic chips with bar code identifiers (A)</p> Signup and view all the answers

What distinguishes electronic gas detectors from gas tube testers according to the text?

<p>Electronic gas detectors use sensors surrounded by sensitive electronics (D)</p> Signup and view all the answers

What is a common limitation of gas tube testers and electronic gas detectors mentioned in the text?

<p>Dependency on proper storage, handling, and disposal (B)</p> Signup and view all the answers

How do electronic gas detectors differ from gas tube testers in terms of the response time for results?

<p>Electronic gas detectors provide quicker results than gas tube testers (C)</p> Signup and view all the answers

What distinguishes small tubes in plastic chips used by certain gas detectors as per the text?

<p>Each tube can only be used once (D)</p> Signup and view all the answers

What is the primary purpose of Intrinsic Safety as mentioned in the text?

<p>Limit energy to prevent ignition of hazardous atmospheric mixtures (A)</p> Signup and view all the answers

Why is it crucial to consider personal protective equipment before conducting any gas testing?

<p>To protect individuals from potential hazards in the atmosphere (B)</p> Signup and view all the answers

Which characteristic defines the ability of direct-reading instruments to provide information quickly?

<p>Response Time (D)</p> Signup and view all the answers

What distinguishes electronic gas detectors in terms of practical use compared to gas tube testers?

<p>Ability to provide real-time continuous monitoring (C)</p> Signup and view all the answers

How does Intrinsic Safety contribute to the selection of gas detection equipment?

<p>It ensures the equipment is safe for use in hazardous locations (B)</p> Signup and view all the answers

Which characteristic is most critical when selecting gas detection equipment tailored to a specific incident?

<p>Detection limit for toxic gases (B)</p> Signup and view all the answers

What factor plays a significant role in ensuring rapid decision-making during mine rescue gas detection?

<p>'Information at the time of sampling' for quick assessment (B)</p> Signup and view all the answers

Why should gas detection equipment be selected based on the specific needs of an incident?

<p>'Effectiveness' in accurately detecting the gases present (B)</p> Signup and view all the answers

When bump testing a gas detector, what is the purpose of exposing the monitor to a known concentration of gas?

<p>To verify the sensor and alarm operation (A)</p> Signup and view all the answers

What should be done if an instrument fails to respond properly during a bump test?

<p>Do a full calibration successfully prior to use (D)</p> Signup and view all the answers

Which type of gases are lighter than air and need to be sampled at different levels within a space according to the text?

<p>Methane (B)</p> Signup and view all the answers

What is the recommended frequency for bump tests on gas detectors according to manufacturers?

<p>Prior to each day's use (B)</p> Signup and view all the answers

What should be visually inspected before using a gas detector as per the 7-5 Steps for Gas Detector Operation?

<p>Damage and contamination (D)</p> Signup and view all the answers

What does 'zeroing the instrument' refer to in gas detector operation?

<p>Adjusting the baseline reading (D)</p> Signup and view all the answers

What is the main purpose of gas detector bump tests?

<p>To verify sensor and alarm operation (C)</p> Signup and view all the answers

What should an operator do if a gas detector fails a bump test?

<p>Conduct a full calibration before using the detector again (A)</p> Signup and view all the answers

What factor in gas detection equipment measures the ratio between the largest and smallest possible signals?

<p>Dynamic Range (B)</p> Signup and view all the answers

Which gas can interfere with gas detection equipment sensors and mask the presence of sulphur dioxide?

<p>Acetylene (D)</p> Signup and view all the answers

What term is used to define the degree to which the measurement of a substance's quantity matches its actual value in gas detection instruments?

<p>Accuracy (A)</p> Signup and view all the answers

What is the primary purpose of considering performance criteria/specifications when selecting gas detection equipment?

<p>To assess the instrument's ability to detect specific gases (B)</p> Signup and view all the answers

Which of the following could interfere with gas detection equipment and potentially mask the presence of certain gases?

<p>Electromagnetic fields (D)</p> Signup and view all the answers

What is a significant advantage of multi-gas detectors over colorimetric tubes?

<p>They can register multiple toxic gases in a single monitor. (A)</p> Signup and view all the answers

What does 'Cross Sensitivity' refer to in relation to gas detection equipment sensors?

<p>Sensor's reaction to an interfering gas (B)</p> Signup and view all the answers

Why is it important for operators to continuously sample the atmosphere while work is being completed?

<p>To provide real-time data on changing gas concentrations. (C)</p> Signup and view all the answers

Which characteristic of gas detection equipment describes how much readings fluctuate when the concentration of a substance remains constant?

<p>Precision (D)</p> Signup and view all the answers

What factor contributes to premature sensor degradation in gas detectors?

<p>Exposure to high humidity levels (B)</p> Signup and view all the answers

What is the purpose of following all manufacturer’s specifications for application and use when selecting gas detection equipment?

<p>To maintain accuracy and performance standards (B)</p> Signup and view all the answers

How do portable field docking stations enhance the usability of some gas detectors?

<p>By allowing for remote monitoring and data transfer (D)</p> Signup and view all the answers

Which gas sensor type has the shortest typical life span according to the information provided?

<p>Photoionization gas sensors (B)</p> Signup and view all the answers

What is an essential requirement before using a multi-gas detector in confined spaces?

<p>Performing a pre-use procedure every time (C)</p> Signup and view all the answers

What is an advantage of multi-gas detectors over gas tube testers in terms of alarms?

<p>Multi-gas detectors offer both low-level and high-level alarms. (B)</p> Signup and view all the answers

Why do many multi-gas detectors have interchangeable-sensor capabilities?

<p>To allow for customization based on specific gas detection needs. (B)</p> Signup and view all the answers

What is a significant difference between small tubes in plastic chips used by certain gas detectors and traditional gas tube testers?

<p>Small tubes are disposable and can only be used once, unlike traditional gas tubes that are reusable. (B)</p> Signup and view all the answers

Which factor plays a significant role in determining the accuracy of colorimetric tube-style gas detectors?

<p>The humidity and temperature conditions during testing (B)</p> Signup and view all the answers

What distinguishes electronic gas detectors from gas tube testers in terms of their portability?

<p>Electronic gas detectors are generally stationary and not designed for portable use like gas tube testers. (D)</p> Signup and view all the answers

Which aspect is crucial for the proper functioning of electronic gas detectors?

<p>The regulated manufacturer standards they meet (A)</p> Signup and view all the answers

Why is it important for electronic gas detectors to have alarms (visual, audible, vibrating)?

<p>To alert operators to the presence of gases when the sensor detects them (A)</p> Signup and view all the answers

Which statement accurately describes the uniqueness of Drager CMS among common types of detectors mentioned?

<p>Drager CMS uses a different chemical reaction principle compared to other detectors. (C)</p> Signup and view all the answers

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Study Notes

Gas Detection Instruments

  • Four categories of hazardous atmospheres:
    • Toxic
    • Oxygen deficiency/Asphyxiating gases
    • Explosive/flammable gases or vapours
    • Smoke, aerosols, fumes (particulate contaminants)

Selecting Gas Detection Equipment

  • Select equipment that fits specific needs of the incident
  • Consider performance criteria/specifications of the instrument:
    • Response Time
    • Noise/Drift
    • Limit of Detection (LOD)
    • Accuracy
    • Precision
    • Dynamic Range
  • Check for conditions that could interfere with the equipment:
    • Cross Sensitivity
    • Electromagnetic fields
    • Humidity
    • Atmospheric pressure/altitude
    • Low temperatures
    • Saturation and high concentrations

Colorimetric (Tube-style) Indicators

  • Measure more than 200 organic and inorganic gases and vapours in the air
  • Advantages:
    • Operation with one hand
    • Low weight and simple operation
    • Always ready for use (no batteries)
    • Tubes for more than 200 different gases and vapours
    • Printed measuring scale on the tubes provides immediate reading of the result
    • Low maintenance
  • Limitations:
    • Tubes and pumps are manufacturer-specific
    • No alarm system, therefore not recommended for continuous monitoring
    • Dependent upon operator’s interpretation of results
    • Application can require longer periods of time in atmospheres for results to appear (up to several minutes)
    • Limited shelf-life
    • Only accurate within +/- 20%
    • Many cross-sensitivities

Electronic Gas Detectors

  • Complex system including a sensor(s) surrounded by sensitive electronics, alarms, battery, and display
  • Advantages:
    • Multi-gas detectors use separate sensors for oxygen and combustible atmospheres
    • Can register multiple toxic gases in the same hand-held monitor
    • Many models have interchangeable-sensor capabilities
    • Will provide low-level and high-level alarms
    • Accidental power-off protection
    • Many are capable of internal data-logging
    • Portable field docking stations are also available for several models
    • Can have an internal motorized pump or a diffusion monitor with attachable pump
    • More accurate than colorimetric tubes – accurate within +/- 10%
  • Limitations:
    • Sensor sensitivity and response to gas will degrade over time; Limited shelf life
    • Gases recognized are sensor-specific
    • Requires time to perform a pre-use procedure
    • Sensors and batteries have a finite life
    • Environmental conditions contribute to premature sensor degradation

Practical Skills for Gas Detection

  • Atmospheric sampling:
    • Follow all manufacturer’s specifications and guidelines
    • Proper sampling techniques due to the stratification of gases that may be present
    • Sample prior to entry, prior to re-entry, and continuously while work is being completed
  • Relative Density:
    • Sample at the top, middle, and bottom of a space
    • Sample every 1–2 metres (3–7 ft) due to the weights of gases

Bump Testing and Calibration

  • Function (“bump”) testing involves a brief exposure of the monitor to a known concentration of gas(es) for the purpose of verifying sensor and alarm operation
  • Calibration involves adjusting the instrument to ensure accuracy
  • Important elements of gas detector maintenance include:
    • Function (“bump”) testing
    • Calibration

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