MLT GlobeLaboratory Operations: Lab safety – page 2
41 Laboratory Operations MCQs on Lab safety with answers and explanations.
In the RACE fire response plan, what does the letter R stand for?
RACE means Rescue, Alarm, Contain (confine) and Extinguish or Evacuate.
In phlebotomy, most needlestick injuries to staff are linked to:
Injuries mostly occur after the procedure, when needles are recapped or left for disposal. Immediate use of safety devices and puncture-resistant sharps containers prevents them.
A laboratory will grow and manipulate cultures of Mycobacterium tuberculosis. The minimum biosafety level required is:
Propagation and manipulation of M. tuberculosis cultures require BSL-3 because of aerosol transmission risk. Preparing smears from clinical specimens may be done under BSL-2 practices in a biosafety cabinet.
Which biological safety cabinet protects the worker and the environment but NOT the product from contamination?
A Class I cabinet draws unfiltered room air across the work surface, so the product is not protected. Class II cabinets supply HEPA-filtered downflow air that protects the product as well.
A totally enclosed, gas-tight biosafety cabinet operated through attached rubber gloves is a:
Class III cabinets (glove boxes) are gas-tight with glove ports and give maximum protection, used for BSL-4 agents. Class I and II cabinets have an open front.
A horizontal laminar-flow clean bench is NOT suitable for handling infectious specimens because it:
A clean bench pushes HEPA-filtered air across the work surface toward the operator. It protects the product only and would expose the worker to aerosols from infectious material.
Under the Globally Harmonized System (GHS), a Safety Data Sheet contains how many standard sections?
GHS and OSHA HazCom 2012 require a 16-section SDS format, for example Section 2 hazard identification and Section 4 first-aid measures.
A small fire starts in a beaker of xylene. In the US classification this is a class:
Class B fires involve flammable liquids and gases such as xylene, alcohol and acetone. Class A is ordinary combustibles, C is energized electrical equipment and D is combustible metals.
For disinfecting a blood spill on a bench after absorbing the bulk material, the commonly recommended agent is household bleach diluted:
A 1:10 dilution of household bleach (about 0.5% sodium hypochlorite), freshly prepared, is recommended for large or organic-rich spills with adequate contact time.
Picric acid used in histology must be stored:
Dry picric acid is shock-sensitive and can form explosive picrates with metals. It is kept wet with water and stored in non-metal containers.
Sodium azide preservative should not be poured down drains in large volumes because it:
Sodium azide reacts with copper and lead plumbing to form shock-sensitive, explosive metal azides. Disposal follows the SDS and local rules, with copious water flushing if permitted.
According to the CDC sequence for removing PPE, which item is usually removed first?
CDC guidance removes the most contaminated item, gloves, first, then goggles/face shield, gown and finally the mask or respirator, followed by hand hygiene.
Under the OSHA bloodborne pathogens standard, the hepatitis B vaccine for an at-risk laboratory employee must be:
Employers must offer HBV vaccination at no cost within 10 working days of initial assignment. Employees may decline but must sign a declination form.
A technologist has a deep needlestick from an HIV-positive patient. Post-exposure prophylaxis should begin:
HIV PEP is most effective when started as soon as possible, ideally within hours and no later than 72 hours. Waiting for later test results reduces its benefit.
A technologist must pour and handle xylene, a volatile toxic solvent. Which engineering control is correct?
A chemical fume hood draws vapours away from the worker and exhausts them. Most Class II A2 cabinets recirculate air through HEPA filters, which do not trap chemical vapours.
Bleach (sodium hypochlorite) should be stored away from acids mainly because mixing them releases:
Hypochlorite reacts with acids to release toxic chlorine gas. Bleach mixed with ammonia produces chloramine vapours, a different hazard.
After handling specimens from a patient with Clostridioides difficile infection, the best hand hygiene method is:
Alcohol does not kill bacterial spores; soap-and-water washing physically removes C. difficile spores. Alcohol rub is otherwise preferred for routine hand hygiene.
A biological safety cabinet should be certified for correct airflow and filter integrity:
Certification is needed at installation, after moving or filter changes, and at least yearly.
Why should the front air grille of a Class II biological safety cabinet not be blocked with papers or equipment?
Room air drawn in through the front grille forms the air curtain that keeps aerosols away from the operator.
The OSHA permissible exposure limit for formaldehyde as an 8-hour time-weighted average is:
OSHA 29 CFR 1910.1048 sets the formaldehyde PEL at 0.75 ppm (8-h TWA), a short-term limit of 2 ppm and an action level of 0.5 ppm.