68 Questions
What term refers to the sensor's reaction to an interfering gas?
Cross Sensitivity
Which factor describes the ability of a sensor to react to its specific gas in a specified time frame?
Response Time
What does 'Limit of Detection (LOD)' represent in gas detection equipment?
The lowest quantity the instrument can detect with confidence
Which term represents the degree to which repeated measurements under unchanged conditions show consistent results?
Precision
What does 'Dynamic Range' measure in gas detection equipment?
Ratio between the largest and smallest possible signals
Which factor defines how much readings fluctuate when the concentration of a substance remains constant?
Noise/Drift
What is the purpose of Intrinsic Safety in gas detection?
To limit energy levels above the required threshold for igniting hazardous atmospheric mixtures
Which category of hazardous atmospheres includes oxygen deficiency and asphyxiating gases?
Oxygen deficiency/Asphyxiating gases
What type of instruments are commonly used in mine rescue gas detection?
Direct-reading instruments
Why is it important to select gas detection equipment tailored to the specific incident's needs?
To facilitate rapid decision-making based on real-time sampling information
What is the primary purpose of direct-reading instruments in gas detection?
To provide information after sampling
What should be considered before conducting any gas testing?
The presence of intrinsically safe personal protective equipment
What is a key advantage of multi-gas detectors?
They use separate sensors for different gases
What is a limitation of using multi-gas detectors?
Their sensor sensitivity degrades over time
How can a multi-gas detector be more versatile in its usage?
By having an internal motorized pump
What is a characteristic of oxygen sensors in terms of lifespan?
1-5 years
Which type of gas sensor has the longest lifespan according to the provided information?
Infrared gas sensors
What is the responsibility of the operator when performing sample tests for gas detection?
Following all manufacturer's specifications and guidelines
What is the purpose of the colorimetric (tube-style) gas detectors mentioned in the text?
To draw a known volume of air through a detector tube designed to measure the concentration of gases and vapors
What should be done before using a colorimetric tube-style gas detector?
Refer to the manufacturer's instructions and perform a pump leak test
How are the readings from colorimetric tubes typically read?
By comparing the color change to a scale printed on the tube
What consideration is important when using short-term indicator tubes?
Comparing the readings to appropriate short-term exposure limits
What is one of the advantages of colorimetric (tube-style) gas detectors mentioned in the text?
Operates with one hand and does not need batteries
Why is it important to store colorimetric tubes properly?
To avoid exposure to excessively low or high temperatures and direct sunlight
What is a major limitation of gas tube testers mentioned in the text?
They have a limited shelf-life
Which of the following is a characteristic of electronic gas detectors as described in the text?
They use plastic chips with bar code identifiers
What distinguishes electronic gas detectors from gas tube testers according to the text?
Electronic gas detectors use sensors surrounded by sensitive electronics
What is a common limitation of gas tube testers and electronic gas detectors mentioned in the text?
Dependency on proper storage, handling, and disposal
How do electronic gas detectors differ from gas tube testers in terms of the response time for results?
Electronic gas detectors provide quicker results than gas tube testers
What distinguishes small tubes in plastic chips used by certain gas detectors as per the text?
Each tube can only be used once
What is the primary purpose of Intrinsic Safety as mentioned in the text?
Limit energy to prevent ignition of hazardous atmospheric mixtures
Why is it crucial to consider personal protective equipment before conducting any gas testing?
To protect individuals from potential hazards in the atmosphere
Which characteristic defines the ability of direct-reading instruments to provide information quickly?
Response Time
What distinguishes electronic gas detectors in terms of practical use compared to gas tube testers?
Ability to provide real-time continuous monitoring
How does Intrinsic Safety contribute to the selection of gas detection equipment?
It ensures the equipment is safe for use in hazardous locations
Which characteristic is most critical when selecting gas detection equipment tailored to a specific incident?
Detection limit for toxic gases
What factor plays a significant role in ensuring rapid decision-making during mine rescue gas detection?
'Information at the time of sampling' for quick assessment
Why should gas detection equipment be selected based on the specific needs of an incident?
'Effectiveness' in accurately detecting the gases present
When bump testing a gas detector, what is the purpose of exposing the monitor to a known concentration of gas?
To verify the sensor and alarm operation
What should be done if an instrument fails to respond properly during a bump test?
Do a full calibration successfully prior to use
Which type of gases are lighter than air and need to be sampled at different levels within a space according to the text?
Methane
What is the recommended frequency for bump tests on gas detectors according to manufacturers?
Prior to each day's use
What should be visually inspected before using a gas detector as per the 7-5 Steps for Gas Detector Operation?
Damage and contamination
What does 'zeroing the instrument' refer to in gas detector operation?
Adjusting the baseline reading
What is the main purpose of gas detector bump tests?
To verify sensor and alarm operation
What should an operator do if a gas detector fails a bump test?
Conduct a full calibration before using the detector again
What factor in gas detection equipment measures the ratio between the largest and smallest possible signals?
Dynamic Range
Which gas can interfere with gas detection equipment sensors and mask the presence of sulphur dioxide?
Acetylene
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?
Accuracy
What is the primary purpose of considering performance criteria/specifications when selecting gas detection equipment?
To assess the instrument's ability to detect specific gases
Which of the following could interfere with gas detection equipment and potentially mask the presence of certain gases?
Electromagnetic fields
What is a significant advantage of multi-gas detectors over colorimetric tubes?
They can register multiple toxic gases in a single monitor.
What does 'Cross Sensitivity' refer to in relation to gas detection equipment sensors?
Sensor's reaction to an interfering gas
Why is it important for operators to continuously sample the atmosphere while work is being completed?
To provide real-time data on changing gas concentrations.
Which characteristic of gas detection equipment describes how much readings fluctuate when the concentration of a substance remains constant?
Precision
What factor contributes to premature sensor degradation in gas detectors?
Exposure to high humidity levels
What is the purpose of following all manufacturer’s specifications for application and use when selecting gas detection equipment?
To maintain accuracy and performance standards
How do portable field docking stations enhance the usability of some gas detectors?
By allowing for remote monitoring and data transfer
Which gas sensor type has the shortest typical life span according to the information provided?
Photoionization gas sensors
What is an essential requirement before using a multi-gas detector in confined spaces?
Performing a pre-use procedure every time
What is an advantage of multi-gas detectors over gas tube testers in terms of alarms?
Multi-gas detectors offer both low-level and high-level alarms.
Why do many multi-gas detectors have interchangeable-sensor capabilities?
To allow for customization based on specific gas detection needs.
What is a significant difference between small tubes in plastic chips used by certain gas detectors and traditional gas tube testers?
Small tubes are disposable and can only be used once, unlike traditional gas tubes that are reusable.
Which factor plays a significant role in determining the accuracy of colorimetric tube-style gas detectors?
The humidity and temperature conditions during testing
What distinguishes electronic gas detectors from gas tube testers in terms of their portability?
Electronic gas detectors are generally stationary and not designed for portable use like gas tube testers.
Which aspect is crucial for the proper functioning of electronic gas detectors?
The regulated manufacturer standards they meet
Why is it important for electronic gas detectors to have alarms (visual, audible, vibrating)?
To alert operators to the presence of gases when the sensor detects them
Which statement accurately describes the uniqueness of Drager CMS among common types of detectors mentioned?
Drager CMS uses a different chemical reaction principle compared to other detectors.
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
Learn about colorimetric (tube-style) gas detectors which measure over 200 organic and inorganic gases and vapors in the air. Understand the pre-use steps, such as performing pump leak tests and ensuring the correct orientation of the detector. Explore how a portable pump draws air for operation.
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