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Authorized Gas Tester (AGT) study materials
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Authorized Gas Tester (AGT) practice questions

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Question 1Properties, hazards and behaviour of gases and vapours

Which physical property explains why methane released in a confined space tends to collect at the highest point?

  1. Its auto-ignition temperature is relatively low
  2. Its flash point is below ambient temperature
  3. Its solubility in water is very low
  4. Its vapour density is lower than that of air Correct answer.

Explanation

A gas whose vapour density (relative to air) is below 1 is buoyant and rises, so methane accumulates at high points and roof spaces. Flash point, auto-ignition temperature and water solubility influence ignition and detection but not buoyancy. Testers therefore sample the roof zone first when methane is suspected.

Question 2Properties, hazards and behaviour of gases and vapours

A flammable gas has a lower explosive limit (LEL) of 5% by volume in air. A meter reading of 1% by volume corresponds to what percentage of the LEL?

  1. 20% LEL Correct answer.
  2. 50% LEL
  3. 5% LEL
  4. 10% LEL

Explanation

Percentage of LEL equals the measured concentration divided by the LEL, multiplied by 100. Here 1% divided by 5% equals 0.2, which is 20% LEL. This conversion is essential because gas testers normally record readings as %LEL rather than % by volume.

Question 3Properties, hazards and behaviour of gases and vapours

What defines the upper explosive limit (UEL) of a flammable gas?

  1. The concentration at which the gas becomes toxic to humans
  2. The concentration at which the gas condenses into a liquid
  3. The concentration above which the mixture is too rich to support combustion Correct answer.
  4. The concentration at which the gas begins to smell noticeable

Explanation

The UEL is the highest concentration of fuel in air that will still propagate a flame; above it the mixture is too fuel-rich to burn. A reading above the UEL does not mean the atmosphere is safe, because dilution by air can bring the mixture back into the flammable range. Odour, toxicity and condensation are separate properties.

Question 4Properties, hazards and behaviour of gases and vapours

Which statement correctly describes the relationship between a liquid's flash point and its fire point?

  1. The fire point is normally a few degrees above the flash point Correct answer.
  2. The fire point is normally a few degrees below the flash point
  3. The fire point applies only to gases, not liquids
  4. The flash point and fire point are always identical

Explanation

The flash point is the lowest temperature at which a liquid gives off enough vapour to flash momentarily when an ignition source is applied. The fire point is slightly higher, being the temperature at which vapour continues to burn after ignition. Testers use flash point to judge whether a liquid can produce a flammable atmosphere at ambient temperature.

Question 5Properties, hazards and behaviour of gases and vapours

Why is hydrogen particularly hazardous when it accumulates in an enclosed space?

  1. It has a very wide flammable range and a very low ignition energy Correct answer.
  2. It has a strong distinctive odour that aids detection
  3. It is heavier than air and pools at floor level
  4. It is completely odourless and has a narrow flammable range

Explanation

Hydrogen is flammable from about 4% to 75% by volume in air and can be ignited by very small energies, including static discharge. It is also buoyant, so it collects at high points. Its lack of colour and odour means only instrument testing can reveal its presence.

Question 6Properties, hazards and behaviour of gases and vapours

Carbon monoxide is dangerous in confined spaces mainly because of which property?

  1. It is colourless, odourless and binds strongly to haemoglobin Correct answer.
  2. It is flammable across a very wide range
  3. It has a pungent smell that causes panic
  4. It is heavier than air and displaces oxygen at low level

Explanation

Carbon monoxide has no colour or smell and combines with haemoglobin far more readily than oxygen, so it can cause unconsciousness without warning. It is slightly lighter than air and mixes readily. Testers rely on direct-reading instruments or detector tubes because the senses cannot detect it.

Question 7Properties, hazards and behaviour of gases and vapours

What is meant by the term 'oxygen deficiency' in the context of entry into a confined space?

  1. An atmosphere in which carbon dioxide is present at any level
  2. An atmosphere containing more than 21% oxygen by volume
  3. An atmosphere containing less than 23.5% oxygen by volume
  4. An atmosphere containing less than 19.5% oxygen by volume Correct answer.

Explanation

Atmospheres below 19.5% oxygen by volume are normally treated as oxygen-deficient and unsafe for entry without breathing apparatus. The figure is a widely applied threshold, not a precise physiological boundary. Oxygen enrichment above 23.5% is a separate hazard.

Question 8Properties, hazards and behaviour of gases and vapours

A gas detector tube is used to measure a specific gas in a confined space. What does the tube's chemical reagent do?

  1. It changes colour in proportion to the amount of gas drawn through it Correct answer.
  2. It generates a small electrical current proportional to gas concentration
  3. It filters out interfering gases before measurement
  4. It converts the sampled gas into a harmless compound

Explanation

Colourimetric detector tubes contain a reagent that reacts with the target gas, producing a colour change whose length or intensity indicates concentration. A known volume of air must be drawn through with a calibrated pump. They are not generators of current or filters.

Question 9Properties, hazards and behaviour of gases and vapours

A reading of 15% LEL is recorded in a vessel that previously contained a flammable solvent. What is the most appropriate interpretation?

  1. The atmosphere is above the normal entry threshold and requires purging and re-testing Correct answer.
  2. The atmosphere is above the UEL and therefore safe from ignition
  3. The reading can be ignored if no odour is detected
  4. The atmosphere is safe to enter because it is below the LEL

Explanation

Many permit systems set a maximum of 10% LEL before entry or hot work, so a 15% LEL reading exceeds the threshold. The correct response is to stop, ventilate or purge, and re-test until the reading falls within the permitted limit. A reading below the LEL is not automatically safe, because pockets and stratification can occur.

Question 10Properties, hazards and behaviour of gases and vapours

Why does carbon dioxide present a hazard in a pit or excavation even though it is not flammable?

  1. It is absorbed by soil and later released as methane
  2. It is denser than air and can accumulate at low level, displacing oxygen Correct answer.
  3. It reacts with air to produce carbon monoxide
  4. It is lighter than air and rises to form a flammable layer

Explanation

Carbon dioxide has a vapour density of about 1.5 relative to air, so it tends to accumulate in low-lying areas such as pits and excavations. At high concentrations it acts as a simple asphyxiant by displacing oxygen. Testing must therefore include low-level oxygen and carbon dioxide measurement.

Question 11Properties, hazards and behaviour of gases and vapours

A flammable vapour has a flash point of 40 degrees Celsius. What does this imply for work at an ambient temperature of 20 degrees Celsius?

  1. The liquid will not normally produce an ignitable vapour concentration at that ambient temperature Correct answer.
  2. The liquid will immediately form a flammable atmosphere at that ambient temperature
  3. The liquid will only become flammable when heated above its auto-ignition temperature
  4. The liquid is incapable of burning under any circumstances

Explanation

A flash point above ambient means the liquid does not readily release enough vapour to form an ignitable mixture at that temperature. However, sprays, mists or heating can still create flammable conditions. Auto-ignition temperature is a different property and is normally much higher.

Question 12Properties, hazards and behaviour of gases and vapours

Which property of a gas determines whether it will be detected more readily at the top or the bottom of a confined space?

  1. Its odour threshold
  2. Its vapour density relative to air Correct answer.
  3. Its lower explosive limit
  4. Its auto-ignition temperature

Explanation

Vapour density relative to air determines buoyancy: gases lighter than air rise and heavier gases sink. This guides the choice of sample points at high and low levels. LEL, auto-ignition temperature and odour threshold affect hazard severity or detectability but not the direction of accumulation.

Question 13Properties, hazards and behaviour of gases and vapours

Why must a gas detector be zeroed in clean air before use in a confined space?

  1. To establish a correct baseline so that small concentrations are not masked by sensor drift Correct answer.
  2. To confirm that the alarm sound is audible
  3. To charge the battery to full capacity
  4. To verify the response time of the sampling pump

Explanation

Zeroing in fresh air sets the instrument's reference point, so residual sensor signal does not appear as a false gas reading or hide a real one. It is distinct from a functional bump test with known gas. Battery, alarm and pump checks are separate pre-use steps.

Question 14Properties, hazards and behaviour of gases and vapours

An atmosphere contains 22% oxygen by volume. What hazard does this represent?

  1. Oxygen enrichment, which increases fire intensity and the risk of clothing ignition Correct answer.
  2. Carbon monoxide poisoning caused by oxygen displacement
  3. Oxygen deficiency, which impairs breathing and judgement
  4. A safe atmosphere suitable for hot work without further testing

Explanation

Concentrations above about 23.5% oxygen by volume are classed as enriched, but 22% already indicates an oxygen level above normal air and warrants investigation. Enrichment makes materials burn faster and more fiercely and can saturate clothing. Deficiency and enrichment are opposite conditions.

Question 15Properties, hazards and behaviour of gases and vapours

Which factor most strongly determines the rate at which a liquid solvent produces flammable vapour in a confined space?

  1. Its vapour pressure at the prevailing temperature Correct answer.
  2. Its density as a liquid
  3. Its electrical conductivity
  4. Its colour and clarity

Explanation

Vapour pressure indicates how readily a liquid evaporates at a given temperature and therefore how quickly a flammable atmosphere can form. Higher temperature raises vapour pressure sharply. Colour, conductivity and liquid density have little bearing on vapour generation.

Question 16Properties, hazards and behaviour of gases and vapours

A confined space contains a mixture at 40% LEL that is then diluted with fresh air. What happens to the concentration as dilution continues?

  1. It immediately falls below the LEL without entering the flammable range
  2. It rises above the UEL and becomes non-flammable
  3. It remains constant because LEL is a fixed value
  4. It passes through the flammable range and then falls below the LEL Correct answer.

Explanation

Diluting a fuel-rich or mid-range mixture reduces its concentration through the flammable range before it drops below the LEL. This is why purging must be monitored continuously rather than assumed to be safe at any intermediate point. The LEL itself is a fixed property of the gas, but the measured concentration changes.

Question 17Properties, hazards and behaviour of gases and vapours

Why is the auto-ignition temperature of a gas important when selecting equipment for a confined space?

  1. Equipment surfaces must not exceed a temperature that could ignite the gas without a spark Correct answer.
  2. It sets the maximum concentration allowed before entry
  3. It indicates the gas's solubility in water
  4. It determines the response time of the detector

Explanation

Auto-ignition temperature is the temperature at which a gas ignites spontaneously without an external ignition source. Equipment used in hazardous areas must have a maximum surface temperature below this value, with a safety margin. It does not define entry concentration limits or detector performance.

Question 18Properties, hazards and behaviour of gases and vapours

Which statement best explains why oxygen displacement by an inert gas such as nitrogen is dangerous during confined space work?

  1. Nitrogen reacts with moisture in the lungs to form an acid
  2. The atmosphere can become oxygen-deficient without any warning odour or colour Correct answer.
  3. Nitrogen is heavier than air and therefore always collects at the bottom
  4. Nitrogen is flammable and can ignite at low concentrations

Explanation

Nitrogen is colourless and odourless, so as it displaces oxygen there is no sensory warning before unconsciousness can occur. This is why continuous oxygen monitoring is required during inerting or purging. Nitrogen is not flammable and does not form acids in the lungs.

Question 19Properties, hazards and behaviour of gases and vapours

A gas detector with a catalytic bead sensor is used to measure a flammable gas. Which condition can cause a falsely low reading?

  1. The absence of sufficient oxygen at the sensor Correct answer.
  2. A concentration above the LEL
  3. A freshly charged battery
  4. The presence of an audible alarm

Explanation

Catalytic sensors rely on combustion at the bead, which needs oxygen; in oxygen-deficient atmospheres the response falls and readings can be misleadingly low. Very high gas concentrations can also saturate or poison the sensor. Alarm state and battery charge do not depress the reading.

Question 20Properties, hazards and behaviour of gases and vapours

Why can a flammable atmosphere form above a liquid whose bulk temperature is below its flash point?

  1. The flash point falls to zero whenever the liquid is agitated
  2. The LEL of the vapour decreases to zero at low temperature
  3. Oxygen is consumed by the liquid, leaving only fuel
  4. Atomised droplets or a warm surface can raise the local vapour concentration above the LEL Correct answer.

Explanation

Spraying, misting or contact with a hot surface can produce vapour locally at concentrations within the flammable range even when the bulk liquid is below its flash point. This is why spraying solvents and hot work near liquids require extra caution. Flash point is not altered by agitation, and oxygen is not removed by the liquid.

Question 21Properties, hazards and behaviour of gases and vapours

A confined space has a reading of 8% LEL at the top and 2% LEL at the bottom. Which conclusion is most defensible?

  1. A gas lighter than air is present and the top is the worst-case sample point Correct answer.
  2. A gas heavier than air is present and the bottom is the worst-case sample point
  3. The atmosphere is safe because both readings are below 10% LEL
  4. The readings are inconsistent and the instrument must be faulty

Explanation

The higher concentration at the top indicates a buoyant gas with a vapour density below that of air. Sampling strategy should target the highest reading zone and continue monitoring there. A single low reading elsewhere does not prove the whole space is safe.

Question 22Properties, hazards and behaviour of gases and vapours

Which property of a vapour explains why a heavier-than-air solvent can remain hazardous in a sump long after the liquid has been removed?

  1. Its vapour density causes it to persist in low-lying areas with limited ventilation Correct answer.
  2. Its flash point rises as the liquid is removed
  3. Its auto-ignition temperature falls over time
  4. Its LEL increases as the vapour ages

Explanation

Heavier-than-air vapours can linger in sumps and pits because natural ventilation is poor at low level. The liquid's removal does not remove the vapour already present. Flash point, auto-ignition temperature and LEL are intrinsic properties that do not change in the way described.

Question 23Properties, hazards and behaviour of gases and vapours

A gas has a flammable range of 2% to 10% by volume in air. A reading of 12% by volume is recorded. What is the correct interpretation?

  1. The mixture is non-flammable under all circumstances
  2. The mixture is above the UEL and too rich to burn, but dilution could bring it into the flammable range Correct answer.
  3. The mixture is at its most explosive concentration
  4. The mixture is safely below the LEL and can be entered without further action

Explanation

A concentration above the UEL is too fuel-rich to propagate a flame, but it is not safe: ingress of air during entry or ventilation can dilute it back through the flammable range. The most explosive concentration is near the stoichiometric point within the range, not above the UEL.

Question 24Properties, hazards and behaviour of gases and vapours

Why is a bump test with a known gas mixture performed before relying on a gas detector in a confined space?

  1. It calibrates the detector to the exact concentration of the test gas
  2. It confirms that the sensor and alarm respond correctly to a gas challenge Correct answer.
  3. It cleans the sensor of contaminants accumulated during storage
  4. It measures the oxygen content of the ambient air

Explanation

A bump test briefly exposes the sensor to a known concentration to verify that it responds and that alarms activate. It is a functional check, not a full calibration, which adjusts the instrument's output. Cleaning and ambient oxygen measurement are separate activities.

Question 25Properties, hazards and behaviour of gases and vapours

Which property of a gas is described by its lower explosive limit (LEL)?

  1. The minimum concentration in air that will support combustion when an ignition source is present Correct answer.
  2. The concentration at which the gas will spontaneously ignite without any ignition source
  3. The maximum concentration at which combustion can still be sustained in air
  4. The concentration at which the gas becomes toxic to a person breathing it

Explanation

The lower explosive limit is the leanest mixture of fuel in air that can still propagate a flame, so below it the mixture is too fuel-lean to burn. It is a flammability boundary, not a toxicity or ignition-temperature value. The upper explosive limit marks the rich boundary of the flammable range.

Question 26Properties, hazards and behaviour of gases and vapours

Two gases have vapour densities of 0.6 and 1.8 relative to air. Where would you expect each to accumulate in a still, unventilated chamber?

  1. Both gases would tend to collect near the roof of the chamber
  2. The 0.6 gas near the roof and the 1.8 gas near the floor Correct answer.
  3. Neither gas would stratify, because vapour density does not affect where a gas collects
  4. The 0.6 gas near the floor and the 1.8 gas near the roof

Explanation

Vapour density compares the molar mass of a gas with that of air, taken as about 1. A value below 1 means the gas is lighter than air and tends to rise, while a value above 1 means it is heavier and tends to settle at low points. In a still space this stratification determines where sampling points should be placed.

Question 27Properties, hazards and behaviour of gases and vapours

A sealed vessel is purged with nitrogen until the oxygen reading is 6% by volume. What is the principal hazard if a worker enters without breathing apparatus?

  1. The atmosphere cannot support life and will cause rapid loss of consciousness Correct answer.
  2. The nitrogen will react with moisture in the lungs to form an acid
  3. The nitrogen will raise the body temperature through a chemical reaction
  4. The atmosphere is immediately flammable because nitrogen is a fuel gas

Explanation

At 6% oxygen the atmosphere is far below the roughly 19.5% needed for normal respiration, and unconsciousness can occur within seconds to minutes without warning symptoms. Nitrogen is inert and simply dilutes the oxygen. Entry therefore requires supplied-air breathing apparatus and continuous atmospheric monitoring.

Question 28Properties, hazards and behaviour of gases and vapours

A liquid has a flash point of 12 degrees Celsius and is handled in a vessel at 30 degrees Celsius. Which statement best describes the flammable hazard in the headspace?

  1. A flammable atmosphere can form because the liquid is above its flash point, giving a vapour concentration at or above the LEL Correct answer.
  2. The headspace is safe because the vapour concentration will always exceed the upper explosive limit
  3. No flammable atmosphere can form because the liquid is below its boiling point
  4. A flammable atmosphere can form only if the vessel is heated above the auto-ignition temperature

Explanation

When the bulk liquid temperature exceeds the flash point, the liquid can release enough vapour to reach the lower explosive limit in the air above it. The headspace is therefore at risk of being flammable at ambient conditions. Boiling point and auto-ignition temperature are not the criteria for this assessment.

Question 29Properties, hazards and behaviour of gases and vapours

A gas has a relative vapour density of 2.5 and a flammable range of 4% to 16% by volume in air. Which combination of sampling position and interpretation is most appropriate for a sump 3 metres deep?

  1. Sample at the bottom of the sump and treat a reading of 2% as non-flammable but still investigate it Correct answer.
  2. Sample at the top of the sump and expect the gas to be absent at the bottom
  3. Sample only at mid-depth and accept readings up to 16% as safe
  4. Sample at the top of the sump and treat any reading below 4% as flammable

Explanation

A vapour density of 2.5 means the gas is much heavier than air and will tend to collect at the lowest point, so sampling at the bottom is essential. A reading of 2% is below the lower explosive limit of 4% and so is not itself flammable, but it indicates a source and possible accumulation, so it warrants investigation and continued monitoring.

Question 30Properties, hazards and behaviour of gases and vapours

A technician uses a detector with a correction factor of 0.5 for a particular gas, but the instrument is set to read directly as if for the calibration gas. The display shows 20% LEL. What is the best interpretation?

  1. The true concentration is about 10% LEL, so the atmosphere is safer than displayed
  2. The true concentration is about 40% LEL, so the atmosphere is more hazardous than displayed Correct answer.
  3. The correction factor has no effect on the displayed reading and can be ignored
  4. The displayed reading already accounts for the factor and is the true concentration

Explanation

A correction factor adjusts the instrument response for a gas other than the calibration gas. If the factor is 0.5 and the instrument is not applying it, the displayed value must be divided by the factor, giving about 40% LEL, which is more hazardous than shown. Failing to apply correction factors can therefore seriously underestimate risk.

Question 31Legislation, standards, roles and responsibilities

Under the UK's confined space legislation, which duty falls on the person who commissions work in a confined space before anyone enters?

  1. To personally accompany every entrant for the whole duration of the work
  2. To avoid entry so far as is reasonably practicable and, where entry is unavoidable, to ensure a safe system of work is in place Correct answer.
  3. To notify the emergency services before each individual entry
  4. To issue gas detectors to all employees regardless of whether entry occurs

Explanation

Confined space law places a hierarchy of duties on those who arrange the work: first avoid entry, then control the risks where entry cannot be avoided by means of a suitable and sufficient assessment and a safe system of work. The duty holder must plan testing, isolation, ventilation and rescue arrangements before entry is permitted.

Question 32Legislation, standards, roles and responsibilities

In the UK permit-to-work regime for confined space entry, who is normally authorised to certify that gas testing has been completed and the space is safe to enter?

  1. Any member of the workforce who happens to be on site
  2. The emergency rescue team leader
  3. The Authorised Gas Tester acting within the limits of the permit Correct answer.
  4. The site security officer on duty

Explanation

The permit identifies named, competent persons and defines the scope of their authorisation. The gas tester certifies test results and entry conditions only within that authorised scope. Signing outside the permit's limits or after it has expired removes the authority.

Question 33Legislation, standards, roles and responsibilities

What is the primary purpose of an entry permit for a confined space?

  1. To record the names of everyone who has ever worked in the space
  2. To replace the need for a risk assessment for routine entries
  3. To document that identified hazards have been controlled and to authorise entry for a defined period Correct answer.
  4. To satisfy insurers by producing a written record at the end of the year

Explanation

A permit is a formal control that records the precautions taken, the test results, the persons authorised and the time limits, and authorises entry only while those conditions persist. It supplements, and never replaces, the risk assessment.

Question 34Legislation, standards, roles and responsibilities

A gas tester is asked to enter a sewer chamber alone to take readings. Which statement best reflects the legal and good-practice position on lone working in confined spaces?

  1. Lone entry is acceptable only where the space has been ventilated for an hour
  2. Lone entry is acceptable if the entry lasts less than five minutes
  3. Lone entry should be avoided because no one could raise the alarm or assist if the tester collapsed Correct answer.
  4. Lone entry is acceptable provided the tester carries a personal detector

Explanation

Confined space entry requires arrangements for rescue and for summoning help, which lone working undermines because a collapsed entrant cannot self-rescue or call for assistance. Attendants or standby persons are normally required outside the space.

Question 35Legislation, standards, roles and responsibilities

Which document should the gas tester consult to confirm the acceptable oxygen concentration and toxic gas limits for a specific entry?

  1. The manufacturer's warranty for the gas detector
  2. The company's annual training plan
  3. The general site induction booklet
  4. The site's risk assessment and associated entry documentation Correct answer.

Explanation

The risk assessment and permit set the specific acceptance criteria for the space, including oxygen range and toxic exposure limits. These criteria reflect the hazards identified and the standards applicable to the site.

Question 36Legislation, standards, roles and responsibilities

What does the role of 'standby person' (also called the attendant) primarily involve during a confined space entry?

  1. Testing the atmosphere inside the space while the entrant works
  2. Completing the permit paperwork after the shift ends
  3. Entering the space to assist with the work when the entrant is busy
  4. Maintaining communication, controlling entry and initiating rescue without entering Correct answer.

Explanation

The standby person remains outside, maintains communication with entrants, controls access at the entry point and raises the alarm or starts rescue arrangements. The standby does not normally enter the space to perform rescue unless trained and equipped for it.

Question 37Legislation, standards, roles and responsibilities

Which of the following best describes the meaning of 'competent person' in the context of gas testing?

  1. Anyone who has worked in the industry for more than ten years
  2. A person holding a degree in chemistry
  3. A person with sufficient training, experience and knowledge to perform the task safely and correctly Correct answer.
  4. A person nominated by the trade union

Explanation

Competence combines training, practical experience and knowledge so that the person can carry out the task correctly and recognise when conditions are outside their limits. It is task-specific and must be demonstrable, not assumed from tenure or qualifications alone.

Question 38Legislation, standards, roles and responsibilities

A permit states that entry is authorised for 'atmospheric testing and inspection only, maximum 30 minutes'. The gas tester is asked to allow a welding crew to enter under the same permit. What is the correct action?

  1. Refuse and refer the change to the permit issuer, since hot work is outside the authorised scope Correct answer.
  2. Allow entry because the atmosphere has already been tested as safe
  3. Allow entry for ten minutes only to stay within the time limit
  4. Allow entry if the welder brings a personal detector

Explanation

A permit authorises only the work described within it; hot work introduces ignition and fume hazards requiring additional controls and often a separate hot work permit. The gas tester must stop and refer the change to the issuer rather than extend the permit informally.

Question 39Legislation, standards, roles and responsibilities

During entry, the gas tester notices that a colleague has altered the permit's gas test readings to show a higher oxygen level than was measured. What should the tester do?

  1. Ignore it because the atmosphere was probably still safe
  2. Initial the altered figures to show agreement
  3. Quietly correct the figures later at the end of the shift
  4. Report the falsification to the permit issuer and stop the entry until the true readings are recorded Correct answer.

Explanation

Falsifying test results undermines the entire permit system and may put lives at risk; the tester must report it and ensure entry does not proceed on false information. Accurate records are a core professional duty of the gas tester.

Question 40Legislation, standards, roles and responsibilities

A contractor arrives on site with a permit signed by a supervisor who is not listed on the site's authorised signatory register. How should the gas tester respond?

  1. Decline to test under the permit until it is validated by an authorised signatory Correct answer.
  2. Proceed because a supervisor signed it
  3. Proceed but note the issue at the end of the job
  4. Proceed if the contractor is experienced

Explanation

Only persons named on the authorised signatory register can issue a valid permit; an invalid permit provides no authority to enter. The tester should decline until the permit is properly authorised.

Question 41Legislation, standards, roles and responsibilities

Which statement correctly describes the relationship between a risk assessment and a permit-to-work for confined space entry?

  1. The risk assessment is only needed if the space is deeper than two metres
  2. The permit is only needed for hot work inside the space
  3. The risk assessment identifies hazards and controls, and the permit translates these into a controlled authorisation for a specific entry Correct answer.
  4. The permit replaces the risk assessment once issued

Explanation

The risk assessment is the analytical basis that identifies hazards and determines controls; the permit applies those controls to a specific task, place and time. Both are required and serve different functions.

Question 42Legislation, standards, roles and responsibilities

What information should a gas tester record on the entry permit after completing atmospheric testing?

  1. The instrument used, its calibration status, the results for each gas tested, and the time of testing Correct answer.
  2. The names of all persons on site that day
  3. Only the highest reading obtained during the test
  4. Only a signature confirming the space is safe

Explanation

A complete record allows verification that the correct instrument, in calibration, was used and that each relevant gas was measured at a known time. This supports later audit and demonstrates the basis for the entry decision.

Question 43Legislation, standards, roles and responsibilities

In the UK, which regulations specifically impose duties for work in confined spaces?

  1. The Confined Spaces Regulations 1997 Correct answer.
  2. The Electricity at Work Regulations 1989
  3. The Provision and Use of Work Equipment Regulations 1998
  4. The Control of Substances Hazardous to Health Regulations 2002

Explanation

The Confined Spaces Regulations 1997 set out the specific duties for confined space work, including avoidance of entry, safe systems of work, and emergency arrangements. Other regulations may also apply, but the confined space duties derive from these Regulations.

Question 44Legislation, standards, roles and responsibilities

The atmosphere in a tank has been tested and found acceptable, but the entry team will be inside for several hours. What should the gas tester recommend?

  1. That continuous or periodic monitoring continues while the space is occupied Correct answer.
  2. That testing resumes only if someone feels unwell
  3. That no further testing is needed once the initial test is passed
  4. That the space be sealed after entry to prevent changes

Explanation

Atmospheres can change due to ongoing work, leaks or desorption, so monitoring must continue throughout occupancy, ideally continuously with alarm-equipped instruments. The initial test establishes a baseline only.

Question 45Legislation, standards, roles and responsibilities

Who is responsible for ensuring that gas detection instruments used for confined space entry are calibrated and within their test interval?

  1. The gas tester who uses the instrument and the employer who provides it Correct answer.
  2. The entrant who will wear the instrument
  3. The instrument manufacturer alone
  4. The site first aider

Explanation

The employer must provide suitable, maintained equipment, and the competent user must verify calibration status and function before use. Responsibility is shared between the provider and the operator, not delegated to others.

Question 46Legislation, standards, roles and responsibilities

A permit has expired at the end of the shift while work in the space is incomplete. What is the correct course of action?

  1. Stop work, withdraw, and revalidate the permit, including fresh testing, before re-entry Correct answer.
  2. Continue only if the gas tester remains on site
  3. Continue working because the space was safe when the shift began
  4. Continue for up to one additional hour as a grace period

Explanation

An expired permit no longer authorises entry; work must stop and the space be vacated. Re-entry requires the permit to be revalidated and the atmosphere retested because conditions may have changed.

Question 47Legislation, standards, roles and responsibilities

What does the term 'authorised gas tester' imply about the scope of the person's authority?

  1. The person may test only within the types of space, gases and conditions for which they are trained and authorised Correct answer.
  2. The person may override the risk assessment when readings are favourable
  3. The person may authorise entry without a permit
  4. The person may test any atmosphere anywhere on any site

Explanation

Authorisation is bounded by training, competence and the employer's written arrangements, which define the spaces, gases and situations the tester may cover. Testing outside that scope requires additional training and authorisation.

Question 48Legislation, standards, roles and responsibilities

A supervisor instructs the gas tester to record a 'pass' result for a space that the tester has not yet tested, to save time on a busy day. What is the appropriate response?

  1. Record the pass and test afterwards if time allows
  2. Ask a colleague to sign the record instead
  3. Record the pass only if the space was tested the previous week
  4. Decline, explaining that a result must reflect an actual test, and test the space before any entry Correct answer.

Explanation

Recording a result that was not obtained is falsification and could lead directly to a fatality if the atmosphere is unsafe. The tester must refuse and perform the test, since professional integrity underpins the whole permit system.

Question 49Legislation, standards, roles and responsibilities

Which of the following is a recognised limitation of a catalytic combustion (pellistor) flammable gas sensor that the gas tester must consider when interpreting results?

  1. It only works in atmospheres above 40 percent oxygen
  2. It measures toxic gas concentrations directly
  3. It may give low or unreliable readings in oxygen-deficient atmospheres or when exposed to certain poisons Correct answer.
  4. It cannot detect any flammable gas at all

Explanation

Pellistor sensors rely on combustion, so they need sufficient oxygen and can be poisoned or inhibited by substances such as silicones or leaded compounds. The tester must know these limits to judge whether readings are trustworthy.

Question 50Legislation, standards, roles and responsibilities

An employer is arranging confined space work and proposes to rely on a generic method statement from a previous project at a different site. What is the correct legal position?

  1. No assessment is needed if the space is shallow
  2. The method statement is acceptable because it was written for confined space work
  3. The method statement is acceptable if signed by a manager
  4. A site-specific risk assessment is required because hazards and conditions differ between sites Correct answer.

Explanation

The risk assessment must be suitable and sufficient for the actual work and conditions, which vary with the space, its contents, adjacent plant and the task. A generic document from another site cannot demonstrate that the specific risks have been considered.