Questions

Laboratory Biosafety — Questions

Study questions for Laboratory Biosafety.

Mock Exam mode

Sit this set one question at a time. Multiple-choice questions mark themselves; written questions reveal a tickable mark scheme so you can score your own answer. You get a combined score at the end.

15 questions: 13 MCQ, 2 written.

High-priority (past-paper) questions only

Universal precautions govern the response: the sample is treated as infectious throughout, and the sequence is deliberate rather than hurried.

Evacuate and warn: clear people from the immediate area and alert nearby staff.
Allow aerosols to settle: do not rush back in; wait for airborne particles to disperse, longer where there is no central exhaust.
Assess exposure and notify: refer anyone splashed or otherwise exposed for medical evaluation, and inform the supervisor and biosafety officer.
Decontaminate in PPE: wearing personal protective equipment (PPE), meaning gloves, a gown and eye protection, cover the spill with absorbent material and apply a suitable disinfectant working from the outside inward.
Contact time and clear-up: leave the disinfectant for its full contact time, then remove the material, wipe the surface again, and discard everything as infectious waste.

a. Primary purpose. A Class II biological safety cabinet contains infectious aerosols and gives three-way protection: it shields the operator and the environment while also protecting the specimen from contamination.

b. Airflow principles. Inward air at the front aperture carries aerosols away from the operator; a curtain of high-efficiency particulate air (HEPA) filtered air flowing downward protects the work surface; and HEPA-filtered exhaust protects the environment before air is recirculated or ducted away.

c. Limitation. A Class II Type A cabinet is not a chemical fume hood and does not clear volatile chemicals; its protection is also easily degraded by draughts, rapid arm movements or poor positioning, so it never replaces good microbiological technique.

A high-efficiency particulate air (HEPA) filter removes at least 99.97% of particles at 0.3 micrometres, the most penetrating particle size, and captures larger and smaller particles even more efficiently.

It does not remove gases or vapours, and it captures viral-sized particles, not only bacteria.

A routine diagnostic specimen for HIV testing travels as Category B under UN3373, “Biological substance, Category B”, packed to packing instruction P650.

Category A (UN2814) is reserved for cultures and the most dangerous agents, UN2900 applies to animal-only pathogens, and the specimen is neither exempt nor unregulated.

A Class II Type A cabinet recirculates most of its air after high-efficiency particulate air (HEPA) filtration, and HEPA does not trap chemical vapour, so flammable or toxic volatiles build up and are returned to the room. Such work needs a fume hood or a total-exhaust cabinet.

A Class II cabinet does protect the operator, does carry HEPA filters, and is not restricted to one risk group.

Contaminated sharps go directly into a puncture-resistant container and are treated as infectious waste, never recapped, reused or landfilled untreated. Needles are not re-covered by hand, which is a leading cause of needlestick injury.

Bagging with general waste, recapping, recycling or flushing all risk injury or release.

PPE sits at the bottom of the hierarchy of controls: it protects only the wearer, and only when correctly used, so it is applied after elimination, engineering and administrative controls, not instead of them.

Treating PPE as the first or sole control, or as better than removing the hazard, inverts the hierarchy.

The itemised list of contents is placed between the secondary packaging and the rigid outer packaging, where it stays legible and protected yet clear of any leak from the primary receptacle. Absorbent material, by contrast, is wrapped around the primary receptacle to soak up a spill.

Placing the list with the specimen, hiding it inside the primary, or omitting it would breach the packaging rules.

When classification is uncertain, the employer performs a risk assessment and provisionally assigns the higher of the groups in question, then notifies the chief inspector. Any human virus not yet assessed defaults to at least group 2.

Defaulting to group 1, assuming harmlessness, or classifying by volume would all understate the hazard.

Universal precautions treat all blood and specified body fluids as though infectious for bloodborne viruses such as HIV and hepatitis B, regardless of the known or suspected diagnosis. Standard precautions extend the same logic to all body fluids, non-intact skin and mucous membranes.

Selective care based on known status, or substituting gloves for hand hygiene, defeats the purpose.

The defining features of a group 4 agent are ready person-to-person transmission and the absence of effective prophylaxis or treatment, which together justify maximum containment. A group 3 agent may cause severe disease but spreads less readily and has available countermeasures.

Size, host range and severity alone do not set the group, and no group 4 agent is worked on the open bench.

A biological indicator, spores of Geobacillus stearothermophilus, is the test that proves sterilisation, because it confirms the cycle killed a highly heat-resistant organism.

Autoclave tape, pressure and run time show only that a load was processed, not that it was rendered safe.

Marburg virus is a risk group 4 agent: it causes severe viral haemorrhagic fever, transmits readily from person to person, and has no established curative treatment or licensed vaccine.

Hepatitis B, cytomegalovirus, respiratory syncytial virus and rotavirus are handled at lower containment as risk group 2 agents.

A Class I cabinet draws room air inward across the work and exhausts it through a high-efficiency particulate air (HEPA) filter, protecting the operator and environment but not the specimen, because unfiltered room air passes over the work surface.

Product protection is the Class II feature, and the sealed-glovebox description belongs to Class III.

Real risk is the agent plus the procedure, the operator’s competence and the environment, so the same virus can be safe in a sealed molecular assay yet hazardous in open high-volume culture. This is why the modern framework matches containment through a risk assessment rather than mapping risk group straight to biosafety level.

The other options misstate how risk grouping and containment relate.

High prioritySAQDiscuss the procedure to follow when a spill of a high-titre HIV viral-load sample occurs in the laboratory. [5]
Model answer
Universal precautions govern the response: the sample is treated as infectious throughout, and the sequence is deliberate rather than hurried.
- Evacuate and warn: clear people from the immediate area and alert nearby staff.
- Allow aerosols to settle: do not rush back in; wait for airborne particles to disperse, longer where there is no central exhaust.
- Assess exposure and notify: refer anyone splashed or otherwise exposed for medical evaluation, and inform the supervisor and biosafety officer.
- Decontaminate in PPE: wearing personal protective equipment (PPE), meaning gloves, a gown and eye protection, cover the spill with absorbent material and apply a suitable disinfectant working from the outside inward.
- Contact time and clear-up: leave the disinfectant for its full contact time, then remove the material, wipe the surface again, and discard everything as infectious waste.
High prioritySAQRegarding the use of a Class II biological safety cabinet (BSC) for aerosol-transmissible pathogens: a. State its primary purpose. [2] b. Explain the airflow principles that protect the operator, the product and the environment. [3] c. Give one limitation relevant to a risk assessment. [1]
Model answer
a. Primary purpose. A Class II biological safety cabinet contains infectious aerosols and gives three-way protection: it shields the operator and the environment while also protecting the specimen from contamination.

b. Airflow principles. Inward air at the front aperture carries aerosols away from the operator; a curtain of high-efficiency particulate air (HEPA) filtered air flowing downward protects the work surface; and HEPA-filtered exhaust protects the environment before air is recirculated or ducted away.

c. Limitation. A Class II Type A cabinet is not a chemical fume hood and does not clear volatile chemicals; its protection is also easily degraded by draughts, rapid arm movements or poor positioning, so it never replaces good microbiological technique.
MCQ
A HEPA filter in a biological safety cabinet is specified to remove what?
- A. All particles larger than 5 micrometres only
- B. At least 99.97% of particles at 0.3 micrometres
- C. Exactly half of the particles of every size
- D. Only bacteria, allowing all viruses to pass
- E. Chemical vapours and gases from the airstream
Show answer
Correct answer: B
A high-efficiency particulate air (HEPA) filter removes at least 99.97% of particles at 0.3 micrometres, the most penetrating particle size, and captures larger and smaller particles even more efficiently.

It does not remove gases or vapours, and it captures viral-sized particles, not only bacteria.
MCQ
A serum sample is couriered to another laboratory for routine HIV viral-load testing. How is it classified for transport?
- A. Category B, UN3373
- B. Category A, UN2814
- C. An exempt human specimen
- D. A non-regulated substance
- E. Category A, UN2900
Show answer
Correct answer: A
A routine diagnostic specimen for HIV testing travels as Category B under UN3373, “Biological substance, Category B”, packed to packing instruction P650.

Category A (UN2814) is reserved for cultures and the most dangerous agents, UN2900 applies to animal-only pathogens, and the specimen is neither exempt nor unregulated.
MCQ
A worker needs to use a volatile flammable solvent at the bench. Why is a standard Class II Type A cabinet unsuitable?
- A. It provides no protection to the operator at all
- B. It cannot be fitted with any HEPA filter
- C. It is reserved exclusively for risk group 4 agents
- D. It removes chemical vapour more effectively than a fume hood
- E. It recirculates air and does not clear volatile chemicals
Show answer
Correct answer: E
A Class II Type A cabinet recirculates most of its air after high-efficiency particulate air (HEPA) filtration, and HEPA does not trap chemical vapour, so flammable or toxic volatiles build up and are returned to the room. Such work needs a fume hood or a total-exhaust cabinet.

A Class II cabinet does protect the operator, does carry HEPA filters, and is not restricted to one risk group.
MCQ
How should contaminated sharps be discarded in the laboratory?
- A. In a sealed plastic bag together with general waste
- B. Recapped by hand and returned to the original tray
- C. Rinsed and placed with the recyclable glass waste
- D. Flushed into the decontaminated liquid waste stream
- E. Into a puncture-resistant sharps container
Show answer
Correct answer: E
Contaminated sharps go directly into a puncture-resistant container and are treated as infectious waste, never recapped, reused or landfilled untreated. Needles are not re-covered by hand, which is a leading cause of needlestick injury.

Bagging with general waste, recapping, recycling or flushing all risk injury or release.
MCQ
In the hierarchy of controls, personal protective equipment (PPE) is regarded as:
- A. The first measure to apply against any hazard present
- B. The last line, after higher controls fall short
- C. A full substitute for engineering controls
- D. Unnecessary once a risk assessment is done
- E. More effective than eliminating the hazard
Show answer
Correct answer: B
PPE sits at the bottom of the hierarchy of controls: it protects only the wearer, and only when correctly used, so it is applied after elimination, engineering and administrative controls, not instead of them.

Treating PPE as the first or sole control, or as better than removing the hazard, inverts the hierarchy.
MCQ
In the triple-packaging system for an infectious substance, where is the itemised list of contents placed?
- A. Inside the primary receptacle with the specimen
- B. Taped to the outside of the outer package only
- C. Inside the absorbent wrapping of the primary
- D. Between the secondary and the outer packaging
- E. It is not required for infectious substances
Show answer
Correct answer: D
The itemised list of contents is placed between the secondary packaging and the rigid outer packaging, where it stays legible and protected yet clear of any leak from the primary receptacle. Absorbent material, by contrast, is wrapped around the primary receptacle to soak up a spill.

Placing the list with the specimen, hiding it inside the primary, or omitting it would breach the packaging rules.
MCQ
Under the South African regulations, an employer meets a new agent not yet classified into a hazard group. What should be done?
- A. Handle it as group 1 until told otherwise
- B. Halt all laboratory work until the chief inspector responds
- C. Provisionally assign the higher of two possible groups
- D. Record it as untested and take no action
- E. Classify it by the specimen volume involved
Show answer
Correct answer: C
When classification is uncertain, the employer performs a risk assessment and provisionally assigns the higher of the groups in question, then notifies the chief inspector. Any human virus not yet assessed defaults to at least group 2.

Defaulting to group 1, assuming harmlessness, or classifying by volume would all understate the hazard.
MCQ
What is the core assumption of universal precautions?
- A. All blood and body fluids are treated as infectious
- B. Only samples from confirmed HIV patients need special care
- C. Gloves alone remove the need for hand hygiene
- D. Precautions apply only after a positive result
- E. Intact skin contact still requires a respirator
Show answer
Correct answer: A
Universal precautions treat all blood and specified body fluids as though infectious for bloodborne viruses such as HIV and hepatitis B, regardless of the known or suspected diagnosis. Standard precautions extend the same logic to all body fluids, non-intact skin and mucous membranes.

Selective care based on known status, or substituting gloves for hand hygiene, defeats the purpose.
MCQ
What most distinguishes a group 4 hazard agent from a group 3 agent?
- A. Group 4 agents are consistently larger enveloped viruses
- B. Group 4 agents may be worked on the open bench safely
- C. Group 4 agents cause only mild, self-limiting infections
- D. Group 4 agents spread readily and lack effective treatment
- E. Group 4 agents are restricted to animal hosts only
Show answer
Correct answer: D
The defining features of a group 4 agent are ready person-to-person transmission and the absence of effective prophylaxis or treatment, which together justify maximum containment. A group 3 agent may cause severe disease but spreads less readily and has available countermeasures.

Size, host range and severity alone do not set the group, and no group 4 agent is worked on the open bench.
MCQ
Which is used to confirm that an autoclave cycle actually inactivated its load?
- A. A colour change seen on the autoclave tape
- B. The chamber pressure gauge reading
- C. Spores of Geobacillus stearothermophilus
- D. The total run time on the display
- E. The colour of the steam produced
Show answer
Correct answer: C
A biological indicator, spores of Geobacillus stearothermophilus, is the test that proves sterilisation, because it confirms the cycle killed a highly heat-resistant organism.

Autoclave tape, pressure and run time show only that a load was processed, not that it was rendered safe.
MCQ
Which of the following agents falls into risk group 4?
- A. Hepatitis B virus
- B. Marburg virus
- C. Cytomegalovirus
- D. Respiratory syncytial virus
- E. Rotavirus
Show answer
Correct answer: B
Marburg virus is a risk group 4 agent: it causes severe viral haemorrhagic fever, transmits readily from person to person, and has no established curative treatment or licensed vaccine.

Hepatitis B, cytomegalovirus, respiratory syncytial virus and rotavirus are handled at lower containment as risk group 2 agents.
MCQ
Which statement about a Class I biological safety cabinet is correct?
- A. It protects the product but leaves the operator exposed
- B. It requires the operator to work through sealed glove ports
- C. It protects the operator and environment, not the product
- D. It is a gas-tight glovebox used at maximum containment
- E. It filters incoming air but exhausts room air unfiltered
Show answer
Correct answer: C
A Class I cabinet draws room air inward across the work and exhausts it through a high-efficiency particulate air (HEPA) filter, protecting the operator and environment but not the specimen, because unfiltered room air passes over the work surface.

Product protection is the Class II feature, and the sealed-glovebox description belongs to Class III.
MCQ
Why does an agent's risk group not by itself fix the biosafety level of the work?
- A. The procedure, operator competence and environment also shape the risk
- B. The manufacturer alone assigns the containment level that is required
- C. Every risk group 2 agent still demands maximum containment work
- D. Only the specimen volume decides the level of containment needed
- E. Risk grouping applies to bacteria and fungi, not to viruses
Show answer
Correct answer: A
Real risk is the agent plus the procedure, the operator’s competence and the environment, so the same virus can be safe in a sealed molecular assay yet hazardous in open high-volume culture. This is why the modern framework matches containment through a risk assessment rather than mapping risk group straight to biosafety level.

The other options misstate how risk grouping and containment relate.