6 Gas Meter Flashcards
What types of calls require a MultiRAE?
- Gas Leaks
- Natural Gas
- Propane
- Fuel Spills
- Gasoline
- Diesel
- CO Alarms
- Overhaul
- Chemical Release
- Refrigeration Leak
- Unknowns
- Odor, Liquids, Powders
- Confined Space
- Trench
- Shipboard
- Industrial Facilities
None
What does the MultiRAE detect?
- Oxygen - OXY
- Lower Explosive Limits - LEL
- Carbon Monoxide - CO
- Hydrogen Sulfide - H2S
- Volatile Organic Compounds - VOC
- Hydrogen Cyanide - HCN
None
When does the MultiRAE alarm for Oxygen (OXY)?
- Low: 19.5%
- High: 23.5%
None
When does the MultiRAE alarm for Lower Explosive Limits (LEL)
- Low: 10%
- High: 20%
None
When does the MultiRAE alarm for Carbon Monoxide (CO)?
- Low: 35 PPM
- High: 200 PPM
None
When does the MultiRAE alarm for Hydrogen Sulfide (H2S)?
- Low: 10 PPM
- High: 20 PPM
None
When does the MultiRAE alarm for Volatile Organic Compounds (VOC)?
- Low: 50 PPM
- High: 100 PPM
None
When does the MultiRAE alarm for Hydrogen Cyanide (HCN)?
- Low: 4.7 PPM
- High: 25 PPM
None
What can cause oxygen levels to change?
Displacement, when another gas replaces the air reducing the OXY content
None
What is the significance of a 1% decrease on an OXY sensor?
Indicates another gas present at 50,000 PPM
None
What are Volatile Organic Compounds (VOC) detected by?
Photoionization Detector (PID)
None
How does a PID work?
Gas passes a UV lamp, is ionized, charged gas ions flow to plates, current produced, concentration displayed
None
What is the Ionization Potential required for detection by the PID?
Must be lower than the Electron Volts of the Lamp used (10.6 eV)
None
What does the LEL Sensor detect?
Flammable vapors of substances above their flashpoint
None
At what %LEL does the MultiRAE alarm?
At 10% LEL and at 20% LEL
Provides an 80-90% safety factor from flammable atmosphere
What should be done before using the MultiRAE?
Fresh air calibrate at the beginning of every shift
None
What must be avoided during fresh air calibration?
Exhaust, cleaners, and other chemicals that can cause incorrect baseline settings
None
What does the meter display after the fresh air calibration countdown?
Calibration results showing pass or fail of each sensor
If any sensors fail, do not use the meter
What is the recommended metering practice?
Meter low, medium, and high relative to the space at a slow speed
This accounts for the possibility of gas/vapors being heavier, lighter, or equal to air
What should be done if the display shows ‘High’?
Move the meter away from the source and allow it to clear in fresh air
This helps avoid saturating the sensors
What does ‘Bat’ indicate on the MultiRAE display?
The battery needs to be recharged
A completely drained battery will be fully charged after 10 hours
What is the importance of mounting location for the MultiRAE?
It should not be exposed to high temperatures that shorten sensor life
Avoid hanging equipment from the truck mount
How to turn on the MultiRAE?
Hold the Mode button until it powers on
It will start its Warm Up
What is the pump’s draw rate for the MultiRAE?
Roughly 300 cc/minute
Moving too fast may miss gas/vapors
True or False: The MultiRAE can be used to certify an area as ‘clean’.
False
Always use a second meter to verify readings
How does the O2 sensor in the MultiRAE detect oxygen levels?
Uses an electrochemical sensor that measures the electrical current generated by oxygen reduction.
What is the primary method used by the MultiRAE to detect CO?
Electrochemical sensor measures the reaction between CO and the sensor’s electrode.
How does the catalytic bead sensor measure LEL?
Combustible gases burn on the bead, generating heat that changes the bead’s resistance.
How does the MultiRAE detect HCN?
Electrochemical sensor reacts with HCN to produce an electrical signal proportional to the concentration.
How is H2S detected in the MultiRAE?
Electrochemical sensor reacts with H2S to generate a current.
What is the principle behind the PID sensor for VOC detection?
Ultraviolet (UV) light ionizes VOCs, and the resulting current measures concentration.
What does the MultiRAE’s pump do during sampling?
Draws air through the sensors for continuous monitoring.
Fill in the blank: The catalytic bead sensor requires sufficient ________ to accurately measure LEL.
Oxygen.
How does the MultiRAE ensure specificity for each gas?
Each sensor is tuned to respond only to a specific gas or family of gases.
What is the role of the UV lamp in the PID sensor?
Ionizes VOC molecules by breaking chemical bonds with UV energy.
What determines the PID sensor’s ability to detect different VOCs?
The ionization energy of the compound compared to the lamp’s UV energy.
How does the MultiRAE prevent cross-sensitivity between sensors?
Uses chemical filters and sensor-specific electrodes to isolate reactions.
How does temperature compensation work in the MultiRAE sensors?
Sensors adjust readings to account for temperature variations using internal algorithms.
Why does the MultiRAE use multiple sensors for gases like VOCs and CO?
To provide overlapping data and detect cross-contamination or interference.
How does the MultiRAE detect gas mixtures?
Each sensor measures specific gases independently, allowing detection of mixtures.
How does the LEL sensor avoid damage in high gas concentrations?
The device uses protective circuitry to prevent overheating of the catalytic bead.
Why are electrochemical sensors used for toxic gases?
They are highly sensitive and produce direct current proportional to gas concentration.
How does the MultiRAE test for interference in VOC detection?
Cross-checks with other sensors and adjusts readings based on response factors.
What role do filters play in the MultiRAE sampling system?
Remove dust, moisture, and contaminants to protect sensors from fouling.
How does data logging enhance testing accuracy?
Tracks time-stamped readings for post-event analysis and calibration validation.
