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CBRN practice questions

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Question 1CBRN Threat Awareness and Agent Recognition

Which nerve agent is a persistent V-series compound that leaves a long-lasting contact hazard on surfaces?

  1. Sarin
  2. VX Correct answer.
  3. Hydrogen cyanide
  4. Tabun

Explanation

V-series agents such as VX are oily, low-volatility liquids that can remain hazardous on surfaces for days to weeks. G-series agents evaporate much more readily, and hydrogen cyanide belongs to a different agent class entirely.

Question 2CBRN Threat Awareness and Agent Recognition

Sulfur mustard exposure typically produces which clinical pattern?

  1. Immediate burning pain followed by rapid tissue death
  2. Pinpoint pupils, drooling, and muscle twitching within minutes
  3. A symptom-free delay of hours, then redness and blisters Correct answer.
  4. Rapid-onset flaccid paralysis spreading upward from the legs

Explanation

Mustard alkylates tissue slowly, so victims often feel well for hours before erythema and blisters develop. This latent period is a hallmark that separates mustard from agents causing immediate pain or cholinergic signs.

Question 3CBRN Threat Awareness and Agent Recognition

Hydrogen cyanide kills primarily by which mechanism?

  1. Damaging DNA in rapidly dividing cells
  2. Halting cellular use of oxygen at cytochrome oxidase Correct answer.
  3. Blocking acetylcholine at neuromuscular junctions
  4. Destroying the alveolar lining and flooding the lungs

Explanation

Cyanide binds the cytochrome oxidase complex and stops oxidative phosphorylation, so cells cannot use delivered oxygen. Blood and tissues therefore stay oxygenated while the patient deteriorates rapidly.

Question 4CBRN Threat Awareness and Agent Recognition

Which agent is classified as a pulmonary (choking) agent that causes delayed-onset pulmonary edema?

  1. Sulfur mustard
  2. Sarin
  3. Phosgene Correct answer.
  4. Hydrogen cyanide

Explanation

Choking agents injure the alveolar-capillary membrane, producing fluid-filled lungs hours after exposure. Phosgene is the classic example, whereas the other options act on nerves, skin, or cellular respiration.

Question 5CBRN Threat Awareness and Agent Recognition

Bacillus anthracis is best described as which type of biological agent?

  1. A non-spore-forming virus
  2. A yeast-like fungus
  3. A spore-forming bacterium Correct answer.
  4. A protein toxin derived from castor beans

Explanation

Anthrax is caused by a Gram-positive bacterium that forms highly durable spores in the environment. Those spores are the reason anthrax is considered a persistent aerosol threat.

Question 6CBRN Threat Awareness and Agent Recognition

Which unit expresses absorbed radiation dose in the International System (SI)?

  1. Gray Correct answer.
  2. Roentgen
  3. Curie
  4. Becquerel

Explanation

The gray measures absorbed dose, the energy deposited per unit mass of tissue. Becquerel and curie measure activity, while the roentgen measures exposure in air.

Question 7CBRN Threat Awareness and Agent Recognition

Which protective equipment level requires a fully encapsulating chemical-protective suit with self-contained breathing apparatus?

  1. Level A Correct answer.
  2. Level D
  3. Level C
  4. Level B

Explanation

Level A provides the highest respiratory and skin protection: a totally encapsulating suit plus SCBA. Lower levels drop either the encapsulation, the respiratory protection, or both.

Question 8CBRN Threat Awareness and Agent Recognition

The 1995 attack in which a nerve agent was released on the Tokyo subway system involved which agent?

  1. VX
  2. Sarin Correct answer.
  3. Mustard
  4. Tabun

Explanation

The 1995 Tokyo subway attack used sarin released from punctured packages, causing thousands of casualties. It remains the most prominent example of a chemical agent used in a mass-casualty terrorist attack.

Question 9CBRN Threat Awareness and Agent Recognition

A casualty presents with pinpoint pupils, profuse salivation, heavy bronchial secretions, and muscle fasciculations. Which agent class fits best?

  1. Nerve agent Correct answer.
  2. Blister agent
  3. Blood agent
  4. Riot control agent (tear gas)

Explanation

These findings form the cholinergic toxidrome caused by acetylcholinesterase inhibition, with muscarinic and nicotinic effects appearing together. Rapid recognition matters because atropine and an oxime are time-critical.

Question 10CBRN Threat Awareness and Agent Recognition

A worker exposed to sulfur mustard vapor feels well and refuses decontamination because nothing hurts. What is the best explanation for this?

  1. Mustard damage is limited to the eyes and airways
  2. Mustard is harmless unless it contacts broken skin
  3. Mustard injury develops only after a latent period of hours Correct answer.
  4. Mustard vapors are too dilute to cause harm outdoors

Explanation

Mustard binds tissue slowly, so clinical effects lag behind exposure by hours, often 2 to 24. Decontamination must therefore proceed even when the patient is asymptomatic.

Question 11CBRN Threat Awareness and Agent Recognition

Chlorine vapor is roughly 2.5 times denser than air. During a release, where should responders expect vapor to collect?

  1. Along ridgelines and exposed hilltops
  2. Uniformly mixed at every height indoors and outdoors
  3. In low areas such as basements and trenches Correct answer.
  4. Only inside sealed air-conditioned buildings

Explanation

A vapor denser than air sinks and pools in low, poorly ventilated spaces. Responders should avoid basements, pits, and trenches and approach from upwind and higher ground.

Question 12CBRN Threat Awareness and Agent Recognition

Ricin is best characterized by which statement?

  1. A live bacterium spread from person to person
  2. A plant-derived toxin with no antidote Correct answer.
  3. A nerve agent that blocks cholinesterase
  4. A virus that produces a pustular rash

Explanation

Ricin is a protein toxin extracted from castor beans that inhibits protein synthesis and is not contagious. Treatment is supportive because no licensed antidote exists.

Question 13CBRN Threat Awareness and Agent Recognition

Which finding is most characteristic of inhalational anthrax?

  1. Descending flaccid paralysis
  2. Vesicles in a dermatomal band
  3. Cherry-red skin with bitter-almond odor
  4. Widened mediastinum on chest imaging Correct answer.

Explanation

Inhaled spores germinate in mediastinal lymph nodes, producing hemorrhage and edema that widen the mediastinum on imaging. A brief flu-like phase typically precedes rapid deterioration.

Question 14CBRN Threat Awareness and Agent Recognition

Which feature best distinguishes smallpox from chickenpox?

  1. Smallpox lesions are limited to the palms and soles
  2. Smallpox lesions spare the face and concentrate on the trunk
  3. Smallpox lesions are all at the same stage of development Correct answer.
  4. Smallpox lesions appear in crops at different stages

Explanation

Smallpox lesions evolve together, so all are at the same stage in a given body area, and they are deep and centrifugal. Chickenpox lesions appear in successive crops at different stages.

Question 15CBRN Threat Awareness and Agent Recognition

After skin contact with a liquid chemical agent, which action is the immediate priority?

  1. Remove contaminated clothing and flush with water Correct answer.
  2. Apply a bleach solution and wait for a physician
  3. Give atropine before any decontamination
  4. Cover the area with an occlusive dressing

Explanation

Removing clothing eliminates most of the liquid contaminant and flushing with water limits further absorption. Decontamination precedes advanced care because ongoing exposure keeps injuring the patient.

Question 16CBRN Threat Awareness and Agent Recognition

What does M9 chemical detector paper indicate?

  1. The presence of nerve agent vapor in the air
  2. The dose rate of gamma radiation
  3. The identity of a specific biological agent
  4. Contact with liquid nerve or blister agent Correct answer.

Explanation

M9 paper is an adhesive dye-impregnated paper that changes color when wetted by liquid nerve or blister agent. It signals liquid contact only and does not identify the agent or detect vapor.

Question 17CBRN Threat Awareness and Agent Recognition

A radiological dispersal device, or dirty bomb, is expected to produce which primary effect?

  1. Long-term inherited genetic damage across a population
  2. A self-sustaining nuclear chain reaction with a blast wave
  3. Contamination and disruption, not acute casualties Correct answer.
  4. Immediate thermal burns over a wide area

Explanation

An RDD spreads radioactive material with conventional explosives, producing contamination, costly cleanup, and fear rather than prompt radiation injury. The blast effects remain conventional.

Question 18CBRN Threat Awareness and Agent Recognition

Which description fits botulinum intoxication?

  1. Fever with a rapidly spreading pustular rash
  2. Descending flaccid paralysis with normal sensation Correct answer.
  3. Ascending paralysis with loss of sensation
  4. Bloody diarrhea followed by kidney failure

Explanation

Botulinum toxin blocks acetylcholine release at the neuromuscular junction, causing symmetric descending flaccid paralysis. Sensory function stays intact, which helps separate it from other neuropathies.

Question 19CBRN Threat Awareness and Agent Recognition

Which set of observations most strongly suggests a deliberate chemical release rather than an industrial accident?

  1. A smell reported by one person in one room
  2. A slow leak detected by fixed sensors over weeks
  3. A single worker injured near a labeled storage tank
  4. Many casualties with identical unusual signs at one event Correct answer.

Explanation

Multiple casualties with the same distinctive toxidrome appearing together, without an obvious industrial source, is a classic indicator of an intentional release. Industrial accidents usually have a traceable source and a less uniform presentation.

Question 20CBRN Threat Awareness and Agent Recognition

Soman poisoning is especially difficult to treat with oxime reactivators because of which property?

  1. Soman is inactive unless inhaled
  2. Soman does not bind acetylcholinesterase
  3. Soman is destroyed rapidly by sunlight
  4. The inhibited enzyme ages very quickly Correct answer.

Explanation

Aging is the loss of the oxime-reactivatable enzyme state as the agent-enzyme complex dealkylates. Soman ages within minutes, so reactivators must be given almost immediately to be effective.

Question 21CBRN Threat Awareness and Agent Recognition

Why can phosgene exposure go unrecognized until pulmonary edema develops?

  1. It is visible as a dense white cloud at all times
  2. It produces intense tearing that hides other signs
  3. Its odor is mild and it causes little immediate irritation Correct answer.
  4. It has no effect on the lungs until days later

Explanation

Phosgene has a faint hay-like odor and is poorly water soluble, so it penetrates to the alveoli with minimal warning irritation. Pulmonary edema then develops hours later, often after the victim feels recovered.

Question 22CBRN Threat Awareness and Agent Recognition

In acute radiation syndrome, which early finding is most useful for roughly estimating dose?

  1. The size of the pupils after exposure
  2. The number of blisters on the hands
  3. The time from exposure to onset of vomiting Correct answer.
  4. A cherry-red skin color appearing within minutes

Explanation

The shorter the interval between exposure and vomiting, the higher the dose received, and serial lymphocyte counts refine the estimate. This makes early symptom timing a practical triage tool.

Question 23CBRN Threat Awareness and Agent Recognition

An attack leaves a persistent oily residue on a road surface. Which agent and hazard pattern is most consistent?

  1. Phosgene, with a delayed lung hazard for hours
  2. Hydrogen cyanide, with a vapor hazard in low areas
  3. Sarin, with a vapor hazard lasting only minutes
  4. VX, with a contact hazard lasting for days Correct answer.

Explanation

An oily residue that remains hazardous indicates a low-volatility persistent agent such as VX, whose main risk becomes skin contact rather than vapor. Volatile agents would disperse rapidly and leave little residue.

Question 24CBRN Threat Awareness and Agent Recognition

Which statement distinguishes lewisite from sulfur mustard?

  1. Lewisite is a blood agent that blocks oxygen use
  2. Lewisite acts by inhibiting acetylcholinesterase
  3. Lewisite blisters appear only after a 12-hour delay
  4. Lewisite causes immediate pain at the exposure site Correct answer.

Explanation

Lewisite is an arsenical vesicant that causes pain immediately on contact, unlike mustard's hours-long latent period. Both are blister agents, but the timing of symptoms differs sharply.

Question 25CBRN Threat Awareness and Agent Recognition

Thiodiglycol is a common industrial solvent that also serves as a precursor for which chemical agent?

  1. Hydrogen cyanide
  2. Phosgene
  3. Sulfur mustard Correct answer.
  4. Sarin

Explanation

Thiodiglycol is a legitimate industrial chemical that can be converted into sulfur mustard, making it a monitored dual-use precursor. Tracking such chemicals supports nonproliferation and interdiction efforts.

Question 26CBRN Threat Awareness and Agent Recognition

Which of the following organisms is classified as a Category A bioterrorism agent by the U.S. Centers for Disease Control and Prevention?

  1. Coxiella burnetii
  2. Bacillus anthracis Correct answer.
  3. Escherichia coli O157:H7
  4. Vibrio cholerae

Explanation

Category A covers agents that are easily disseminated or transmitted person to person, cause high mortality, and require special action for public health preparedness; the list includes Bacillus anthracis (anthrax), Clostridium botulinum toxin, Yersinia pestis, variola virus, Francisella tularensis, and the viral hemorrhagic fevers. Coxiella burnetii, Vibrio cholerae, and E. coli O157:H7 sit in Category B, which covers agents that are moderately easy to disseminate and cause lower morbidity.

Question 27CBRN Threat Awareness and Agent Recognition

Which type of ionizing radiation requires the least shielding to stop?

  1. Neutrons
  2. Beta particles
  3. Alpha particles Correct answer.
  4. Gamma rays

Explanation

Shielding requirements follow penetrating power, which increases from alpha to beta to gamma and neutrons. Alpha particles are heavy, doubly charged, and lose energy over a very short range, so a sheet of paper or the dead outer layer of skin stops them. Beta particles need a few millimeters of plastic or wood, while gamma rays and neutrons require dense or hydrogen-rich materials.

Question 28CBRN Threat Awareness and Agent Recognition

An unknown liquid contaminates a roadway and remains hazardous for several days, producing casualties who touch the surface long after the release. Which agent best fits this low-volatility, high-persistency profile?

  1. Sarin
  2. Hydrogen cyanide
  3. Chlorine
  4. VX Correct answer.

Explanation

Persistency reflects how long an agent stays hazardous on a surface, and it is inversely related to volatility: a substance that evaporates slowly lingers as a contact hazard. VX is an oily, low-volatility nerve agent that can remain a dermal hazard for days or longer. Sarin, hydrogen cyanide, and chlorine all evaporate or disperse rapidly and behave mainly as short-lived vapor hazards.

Question 29CBRN Threat Awareness and Agent Recognition

For an aerosolized biological agent to deposit deep in the lungs and produce an inhalational infection, the particles should fall within which size range?

  1. 100 micrometers or larger
  2. 25 to 50 micrometers
  3. 10 to 20 micrometers
  4. 1 to 5 micrometers Correct answer.

Explanation

Particles in roughly the 1 to 5 micrometer range behave as respirable particles: they are small enough to bypass the filtering of the upper airway and large enough to deposit in the alveoli. Larger particles are trapped by nasal hairs, mucus, and the mucociliary escalator and are cleared before reaching the lower respiratory tract. This is why an effective aerosol weapon must generate a fine-particle cloud rather than a coarse spray.

Question 30CBRN Threat Awareness and Agent Recognition

Several workers collapse within seconds of entering an industrial enclosure fire, with seizures and profound metabolic acidosis, but without miosis, salivation, or bronchorrhea. Which agent and mechanism best explains this picture?

  1. Chlorine, reacting with airway moisture to form acid
  2. Sarin, causing acetylcholine to accumulate at synapses
  3. Hydrogen cyanide, blocking cytochrome c oxidase Correct answer.
  4. Phosgene, alkylating proteins in the alveolar membrane

Explanation

Abrupt collapse with seizures and severe lactic acidosis in an enclosed fire, without the cholinergic signs of a nerve agent, points to a blood agent. Hydrogen cyanide halts cellular respiration by inhibiting cytochrome c oxidase, so tissues cannot use oxygen and anaerobic metabolism drives lactate up. The absence of miosis and profuse secretions argues against a cholinesterase inhibitor.

Question 31Detection, Identification, and Monitoring

In which operating region does a Geiger–Müller counter produce output pulses whose amplitude is essentially independent of the energy deposited by the incident radiation?

  1. The recombination region
  2. The Geiger plateau region Correct answer.
  3. The ionization chamber region
  4. The proportional counter region

Explanation

On the Geiger plateau each ionizing event triggers a self-propagating avalanche that saturates the anode, so every pulse has nearly the same height. The tube therefore reports count rate only and carries no information about the energy of the incident radiation.

Question 32Detection, Identification, and Monitoring

Which personal monitoring device integrates cumulative radiation dose and must be processed in a reader before the dose value can be retrieved?

  1. An ionization chamber survey meter
  2. A thermoluminescent badge Correct answer.
  3. A sodium iodide search probe
  4. A pancake Geiger–Müller probe

Explanation

A thermoluminescent dosimeter stores trapped charge in a crystalline material and releases it as light when heated in a reader, so the accumulated dose is only known after processing. Survey instruments, by contrast, give a real-time reading and store no personal record.

Question 33Detection, Identification, and Monitoring

M8 chemical detection paper is used by pressing it against a surface because it is designed to detect which of the following?

  1. Chemical agent vapor in ambient air
  2. Ionizing radiation at the surface
  3. Liquid agent droplets and residues Correct answer.
  4. Airborne biological particles

Explanation

M8 paper changes color where it contacts liquid chemical agent droplets or residue, so it is blotted against surfaces rather than hung in air. It is a liquid-agent indicator only and gives no response to vapor, biological material, or radiation.

Question 34Detection, Identification, and Monitoring

A handheld ion mobility spectrometer identifies a chemical by measuring which property?

  1. Ion drift velocity in an electric field Correct answer.
  2. The infrared absorption bands of the vapor
  3. The mass-to-charge ratio of ions in vacuum
  4. The retention time through a capillary column

Explanation

Ion mobility spectrometry pulses ionized sample into a drift tube and times how long the ions take to reach the collector under a uniform electric field against a drift gas. That drift time depends on the ion's size, shape, and charge, and is compared with stored libraries.

Question 35Detection, Identification, and Monitoring

Which method is appropriate for collecting vapor-phase organic chemicals from air onto a solid sorbent for later laboratory analysis?

  1. Exposing a dosimeter badge to the air
  2. Pumping air through a solid sorbent tube Correct answer.
  3. Counting particles with a GM probe
  4. Wiping a container interior with a swab

Explanation

A calibrated pump draws a known volume of air through a sorbent bed, where organic vapor is trapped for later thermal desorption or solvent extraction in the laboratory. The collected mass divided by the air volume gives the airborne concentration.

Question 36Detection, Identification, and Monitoring

Before starting a contamination survey in an unfamiliar building, the surveyor should first take which action?

  1. Record the background count rate in a clean area Correct answer.
  2. Set the alarm threshold very low
  3. Increase detector sensitivity to maximum
  4. Survey the area at walking speed

Explanation

Natural background varies from place to place, so an initial reading in a known-clean location establishes the reference against which later readings are judged. Without that baseline an elevated reading cannot be distinguished from ordinary variation.

Question 37Detection, Identification, and Monitoring

A photoionization detector provides which type of measurement?

  1. A cumulative record of personal dose
  2. Compound-specific identification by mass spectrum
  3. A non-specific total ionizable vapor reading Correct answer.
  4. Selective measurement of one target gas

Explanation

A photoionization detector uses an ultraviolet lamp to ionize any molecule whose ionization potential is below the lamp energy, so it reports a summed response for all such vapors present. It indicates that something is present and how much in total, but not what the compound is.

Question 38Detection, Identification, and Monitoring

Which practice best preserves the evidentiary value of a sample collected during a CBRN response?

  1. Opening the container to check for odors
  2. Sealing, labeling, and documenting each transfer Correct answer.
  3. Storing all samples together in one bag
  4. Transferring the sample to an unmarked container

Explanation

A sample is only as useful as the record that ties it to its origin, so it must be sealed, uniquely labeled, and accompanied by a documented chain of custody from collection onward. Each transfer is recorded so that tampering or mix-ups can be excluded.

Question 39Detection, Identification, and Monitoring

A handheld Raman spectrometer fails to produce a usable spectrum when analyzing a strongly fluorescent orange powder. What is the most likely cause?

  1. The ion mobility cell inside the unit is saturated
  2. Sample fluorescence masks the weak Raman signal Correct answer.
  3. Raman bands are too broad for the spectral library
  4. The instrument requires a vacuum path to the detector

Explanation

Raman scattering is intrinsically very weak, and fluorescent emission from the sample is many orders of magnitude stronger, raising the spectral baseline until the Raman peaks are buried. Longer excitation wavelengths or fluorescence-correction algorithms are the usual remedies.

Question 40Detection, Identification, and Monitoring

Why is mid-infrared spectroscopy poorly suited to measuring analytes dissolved in water?

  1. Water absorbs strongly in the mid-infrared region Correct answer.
  2. Water quenches the infrared detector at room temperature
  3. Water dissolves the diamond ATR crystal on contact
  4. Dissolved analytes cannot absorb infrared light

Explanation

Water has intense absorption bands across the mid-infrared, and because it is present in vast excess over the analyte it dominates the spectrum and masks the analyte bands. Techniques such as attenuated total reflectance with thin sample layers reduce but do not eliminate the problem.

Question 41Detection, Identification, and Monitoring

A laboratory confirms an unknown sample by gas chromatography–mass spectrometry. Which combination of data is compared against a reference library?

  1. Density and refractive index
  2. Color change and pH
  3. Retention time and mass spectrum Correct answer.
  4. Melting point and electrical conductivity

Explanation

Confirmation requires two independent pieces of evidence: the retention time on the column indicates the compound's chromatographic behavior, and the electron-impact mass spectrum indicates its fragmentation pattern. Agreement of both with a library entry is far stronger than either alone.

Question 42Detection, Identification, and Monitoring

Which analytical approach is most suitable for identifying a nonvolatile protein toxin such as ricin in a swab extract?

  1. Gas chromatography with a flame detector
  2. Photoionization with a 10.6 eV lamp
  3. LC–tandem mass spectrometry Correct answer.
  4. Ion mobility spectrometry

Explanation

Large proteins are nonvolatile and thermally labile, so vapor-phase techniques either fail to introduce them or destroy them. Liquid chromatography keeps the analyte in solution and tandem mass spectrometry provides fragment ions that identify the specific peptide sequence.

Question 43Detection, Identification, and Monitoring

A handheld lateral-flow immunoassay gives a positive line for a biological agent. How should that result be handled?

  1. As a false positive to be discarded
  2. As a confirmed identification of the agent
  3. As presumptive, needing confirmatory testing Correct answer.
  4. As proof the agent is absent

Explanation

Handheld immunoassays are screening tools whose antibodies can cross-react with related organisms, so a positive line indicates possible presence only. A reference laboratory must confirm the finding with a method such as molecular or culture-based identification.

Question 44Detection, Identification, and Monitoring

In real-time PCR, a lower cycle threshold (Ct) value indicates which of the following?

  1. A failed amplification reaction
  2. A lower target concentration in the sample
  3. A higher initial target concentration Correct answer.
  4. An inhibitor present in the sample

Explanation

The Ct is the cycle at which fluorescence first crosses the detection threshold, so more starting template means the threshold is reached in fewer cycles. A high Ct therefore reflects a low target amount or partial inhibition, not a stronger signal.

Question 45Detection, Identification, and Monitoring

Which capability distinguishes passive standoff infrared detectors from point detectors?

  1. They identify agents inside containers
  2. They quantify personal dose equivalents
  3. They detect alpha contamination on surfaces
  4. They detect vapor clouds remotely without contact Correct answer.

Explanation

Passive standoff instruments collect infrared energy emitted by a distant vapor cloud against the background and derive a spectrum without sampling the air. They are used to screen an area before responders enter, whereas point detectors must be brought to the contamination.

Question 46Detection, Identification, and Monitoring

An elastic backscatter lidar system operating over a facility can accomplish which of the following?

  1. Identify the specific agent inside the cloud
  2. Detect and range an aerosol cloud remotely Correct answer.
  3. Measure the radiation dose rate at ground level
  4. Confirm the presence of biological DNA in a cloud

Explanation

Elastic lidar fires short laser pulses and times the light scattered back from suspended particles, so it can show that a cloud exists and where it is. Identification requires additional spectral or sampling information that elastic backscatter alone does not provide.

Question 47Detection, Identification, and Monitoring

With a colorimetric detector tube and hand pump, the concentration of a gas is read from which feature?

  1. The time taken for the stain to appear
  2. The total number of pump strokes used
  3. The stained length read against a printed scale Correct answer.
  4. The brightness of the color under UV light

Explanation

A known volume of air is drawn through the tube and the reagent layer is discolored over a length proportional to the amount of target gas present. The user compares that length with the concentration scale printed on the tube.

Question 48Detection, Identification, and Monitoring

The main limitation of a small electrochemical gas sensor deployed in a mixed atmosphere is that it does what?

  1. Is destroyed by high humidity
  2. Cross-responds to other gases in the mixture Correct answer.
  3. Cannot operate at low temperatures
  4. Requires a vacuum pump to draw the sample through

Explanation

An electrochemical cell oxidizes or reduces whatever reaches the sensing electrode, so gases with similar redox behavior produce a current indistinguishable from the target's. Selective filters and correction algorithms reduce but do not eliminate cross-sensitivity.

Question 49Detection, Identification, and Monitoring

A survey meter displaying 20 µSv/h is reporting which quantity?

  1. The activity of the source in becquerels
  2. The ambient dose rate at the probe position Correct answer.
  3. The total dose accumulated by the wearer
  4. The raw counts per minute before calibration

Explanation

The unit µSv/h is a dose per unit time, so the meter is reporting the rate at which dose is being delivered at the probe's location. Multiplying that rate by the time spent in the field gives the accumulated dose.

Question 50Detection, Identification, and Monitoring

When surface contamination is monitored by wipe sampling and the wipe is counted in a laboratory counter, the reported activity should be corrected for which factor?

  1. The barometric pressure recorded in the laboratory
  2. The wipe's recovery efficiency on that surface Correct answer.
  3. The ambient wind speed at the site
  4. The color of the wipe material used

Explanation

A wipe removes only part of the contamination present, and the fraction recovered depends on the surface, the wipe material, and the pressure applied. Without dividing by that recovery efficiency the result underestimates the contamination actually on the surface.