Day 1: Core Concepts + Hardware Flashcards
(28 cards)
What is the primary purpose of a gas detector?
To detect hazardous gases in the environment to protect human life, prevent explosions, ensure compliance with safety regulations, and protect equipment.
What is the difference between a fixed and portable gas detector?
A fixed gas detector is permanently mounted and monitors a specific area continuously, typically wired into a system. A portable gas detector is battery-powered, carried by a worker, and monitors gases on the go.
When would you use a fixed gas detector?
In permanent areas where gas hazards may develop, such as near storage tanks, gas lines, or confined spaces with poor ventilation.
Where would you use a portable gas detector?
For personal protection in variable locations, such as maintenance jobs, confined space entry, or site inspections.
How does a diffusion-based gas detector work?
It passively allows gas to enter the sensor area from surrounding air without any pumps.
How does a sampling-based gas detector work?
It actively draws air through a sampling line or tube using pump to detect gases remotely.
When should a sampling system be used instead of diffusion?
When the gas source is inaccessible or hazardous, such as inside tanks, pits, or ducts.
Where should you mount a detector for a lighter-than-air gas like hydrogen or methane?
Near the ceiling or upper areas of a room.
Where should you mount a detector for a heavier-than-air gas like CO2 or H2S?
Near the floor or in low-lying areas.
Where should a gas detector be mounted for gases like CO or O2?
At breathing zone height, approximately 4-5 feet from the floor.
What are electrochemical sensors used for?
Detecting toxic gases such as CO, H2S, NO2, and NH3.
What are catalytic bead sensors used for?
Detecting combustible gases like methane and propane. Requires oxygen to function.
What are infrared (IR) sensors used for?
Detecting gases like CO2 and hydrocarbons. They do not require oxygen and are immune to sensor poisoning.
What are photoionization detectors (PID) used for?
Detecting volatile organic compounds (VOCs) like benzene, acetone, or paint solvents.
What are metal oxide semiconductor (MOS) sensors used for?
Detecting general gases such as hydrogen, alcohol vapors, and ammonia. Less accurate than other methods.
What is the typical lifespan of an electrochemical gas sensor?
2-3 years, though it varies by manufacturer and gas type.
What factors can shorten a gas sensor’s lifespan?
Exposure to high gas concentrations, humidity, temperature extremes, and lack of calibration or maintenance.
What are signs that a gas sensor needs replacement?
Slow response times, inaccurate readings, or failing zero/span calibrations.
What are common replacement parts for portable gas detectors?
Sensors, duct/moisture filters, batteries, charging docks.
What are common replace parts for fixed gas detectors?
Sensor modules, filters, sampling pumps, display or control boards.
What is a sampling line?
A tube that draws air from a remote or hazardous area to a gas sensor using a pump, allowing for safe gas detection from a distance.
What are some toxic gases and the appropriate sensor?
Carbon monoxide (CO), Hydrogen Sulfide (H2S), Nitrogen Dioxide (NO2), Ammonia (NH3), Chlorine (Cl2), Sulfur Dioxide (SO2)
All of these are detected with electrochemical sensors.
What are some combustible gases and the appropriate sensor?
Methane - CH4 - Catalytic bead or IR sensor
Propane - C3H8 - Catalytic bead or IR sensor
Hydrogen - H2- Catalytic bead or MOS sensor
Butane - C4H10 - Catalytic bead or IR sensor
Ethylene - C2H4 - Catalytic beard or IR sensor
What are some asphyxiant gases and the appropriate sensors?
Carbon Dioxide - CO2 - Infrared (IR) sensor
Oxygen - O - electrochemical sensors (monitors deficiency or enrichment)
Nitrogen - N2 - Measured using oxygen displacement
