MLT GlobeLaboratory Operations: Lab safety
41 Laboratory Operations MCQs on Lab safety with answers and explanations.
Which single measure is most effective in preventing spread of infection in healthcare and laboratory settings?
Hand hygiene breaks the commonest transmission route. Under standard precautions every specimen is treated as infectious, so labelling only known positives gives false security.
A technologist is opening blood tubes at the bench, where splashing may occur. Which PPE combination is appropriate?
Standard precautions require a closed lab coat and gloves for specimen handling, plus eye/face protection (or a splash shield) wherever splashes or aerosols are possible.
Which extinguisher is appropriate for a fire in an electrical instrument (US class C)?
Water and foam conduct electricity and risk electrocution. CO2 or dry chemical extinguishers are used; switch off the power if it is safe to do so. (Class A: ordinary combustibles, B: flammable liquids, D: metals.)
Routine handling of patient blood that may contain hepatitis B virus or HIV requires, at minimum:
Clinical labs handling human blood and body fluids operate at BSL-2 with standard precautions, PPE and biosafety cabinets for aerosol-producing procedures.
On the NFPA 704 hazard diamond, the blue section indicates the:
NFPA 704 uses blue for health, red for flammability, yellow for instability/reactivity and white for special hazards. Each is rated 0 (minimal) to 4 (severe).
When preparing a dilute solution from concentrated sulfuric acid, the correct technique is to:
Adding acid to water lets the large volume of water absorb the heat released. Adding water to acid can boil locally and splash concentrated acid.
A technologist is splashed in the eyes with a corrosive reagent. The immediate action is to:
Eyes should be flushed with water at an eyewash station for at least 15 minutes, holding lids open, then medical evaluation follows. Neutralizing agents can cause further injury.
In the PASS technique for using a fire extinguisher, the letter 'A' stands for:
PASS = Pull the pin, Aim at the base of the fire, Squeeze the handle, Sweep side to side. Aiming at the flames rather than the fuel source is ineffective.
Immediately after a needlestick injury with a used needle, the worker should first:
CDC advises washing the wound with soap and water, then reporting at once so post-exposure evaluation and prophylaxis can start promptly. Squeezing or applying caustic agents is not recommended.
A sharps container in the phlebotomy area should be closed and replaced when it is:
Sharps containers are replaced at about 3/4 full (or at the fill line) to prevent needles protruding and injuries from overfilling.
A fire starts in a container of burning sodium metal. Which extinguisher class is designed for this?
Class D extinguishers (dry powder) are for combustible metals such as sodium, potassium and magnesium. Water can react violently with these metals.
Work with Ebola virus or other agents causing life-threatening disease with no available treatment requires which biosafety level?
BSL-4 is for dangerous exotic agents with high risk of life-threatening disease and no vaccine or treatment, using positive-pressure suits or Class III cabinets. BSL-3 is for agents like M. tuberculosis.
The three basic principles for limiting exposure to ionising radiation in the laboratory are:
Radiation dose is reduced by minimising exposure time, increasing distance from the source and using shielding, following the ALARA principle. PPE alone does not stop penetrating radiation.
A laboratory instrument has a three-prong plug. The third (round) prong is important because it:
The grounding prong carries stray current safely to earth if there is a fault, preventing shock. Surge protection requires separate devices.
To reduce aerosol exposure when centrifuging unstoppered blood tubes, the technologist should:
Sealed buckets or safety cups contain aerosols from broken or open tubes; they should be opened after the rotor stops, preferably in a biosafety cabinet. Opening early releases aerosols.
The international biohazard symbol on waste bags and containers is usually printed in which colour?
Biohazard labels are fluorescent orange or orange-red with the symbol in a contrasting colour, often on red bags.
After a chemical splash to the eyes, they should be flushed at the eyewash station for at least:
Continuous flushing for at least 15 minutes is recommended to remove the chemical, followed by medical review.
A Class II biological safety cabinet protects:
HEPA-filtered downflow and exhaust air in a Class II cabinet protect the sample, the operator and the room.
How should liquids be pipetted in a clinical laboratory?
Mouth pipetting is prohibited because of the risk of swallowing infectious or toxic material.
Before disposal, infectious microbiology waste such as used culture plates is commonly decontaminated by:
Steam sterilisation in an autoclave kills micro-organisms, including spores, before waste leaves the laboratory.