Skip to main content

Cytogenetics

Fire Safety

The cytogenetics laboratory presents a unique fire risk profile compared to other clinical laboratory sections. While automation has reduced some risks, the core chemistry of chromosome preparation involves significant quantities of flammable organic solvents (Methanol, Ethanol, Acetic Acid, Xylene) often used in proximity to heat sources (slide warmers, drying ovens, and historically, open flames). Fire safety training focuses on prevention, proper storage, and immediate response protocols using industry-standard acronyms like RACE and PASS

Classification of Fires

Fire extinguishers and response plans are categorized based on the “fuel” burning. In a cytogenetics lab, the most likely fire types are Class A, B, and C

  • Class A: Ordinary Combustibles
    • Examples: Paper, cardboard boxes, plastic pipette tips, lab coats, trash
    • Extinguishing Agent: Water, Dry Chemical
  • Class B: Flammable Liquids and Gases
    • Examples: Methanol: (the primary component of Carnoy’s fixative), Ethanol, Xylene, Toluene
    • Critical Note: Never use water: on a Class B fire. Water is denser than these solvents; the burning liquid will float on top of the water, spreading the fire further
    • Extinguishing Agent: \(CO_2\), Dry Chemical, Foam
  • Class C: Electrical Equipment
    • Examples: Centrifuges, microscopes, automated harvesters, computer systems, frayed wiring
    • Extinguishing Agent: \(CO_2\), Dry Chemical (Non-conductive). Once the power is cut, it becomes a Class A or B fire

Fire Extinguishers

Laboratories must be equipped with portable fire extinguishers located within 75 feet of any employee. The type of extinguisher must match the hazard

  • ABC Multipurpose Dry Chemical
    • The most common “all-purpose” lab extinguisher
    • Mechanism: Coats the fire with a fine powder (monoammonium phosphate) that separates the fuel from oxygen and interrupts the chemical reaction
    • Disadvantage: It creates a messy, corrosive cloud that can ruin sensitive optics (microscopes) and electronics
  • Carbon Dioxide (\(CO_2\))
    • Often preferred for fires involving expensive electronic equipment or Class B liquids
    • Mechanism: Displaces oxygen and cools the fuel
    • Advantage: Leaves no residue
  • Operation: The PASS Acronym
    • P – Pull: the pin. Break the tamper seal
    • A – Aim: at the base of the fire. Aiming at the flames/top will not extinguish the source
    • S – Squeeze: the handle. This releases the agent
    • S – Sweep: from side to side. Cover the entire base of the fire until extinguished

Emergency Response: The RACE Acronym

When smoke or fire is discovered, the laboratory scientist must act immediately following the RACE protocol

  • R – Rescue: Immediately assist anyone in immediate danger to get out of the area. Do not endanger yourself
  • A – Alarm: Activate the fire alarm system (pull station) and alert the facility (call the emergency number, e.g., “Code Red”)
  • C – Contain: Close all doors and windows to the lab. This limits the oxygen supply to the fire and prevents smoke from entering patient areas or escape routes. (Laboratory doors are usually fire-rated)
  • E – Extinguish/Evacuate
    • Extinguish: Only if the fire is small (size of a trash can), you have the correct extinguisher, and you have a clear exit path behind you
    • Evacuate: If the fire is large or spreading, leave immediately to the designated assembly area

Specific Cytogenetic Hazards & Prevention

Prevention is the primary goal of fire safety. The nature of “harvesting” cells creates specific vulnerabilities

  • Flammable Storage
    • Bulk supplies of Methanol and Acetic Acid must be stored in approved Flammable Safety Cabinets: (yellow, metal, vented)
    • Working Volume: Only a limited amount of flammable liquid (e.g., one day’s supply) should be on the open benchtop
  • The “Alcohol Lamp” Risk
    • Historically, cytogeneticists used open-flame alcohol lamps to heat slides during the “dropping” process to aid chromosome spreading
    • Modern Practice: Most labs have banned open flames. If heat is required, use steam from a water bath or a hot plate. If an open flame is absolutely necessary, it must be used away from the bulk fixative containers
  • Electrical Safety
    • Daisy-chaining (plugging a power strip into another power strip) is a fire code violation often found in labs with too much equipment
    • Frayed cords on centrifuges or water baths must be reported and the equipment tagged “Out of Service” immediately
  • Fixative Mixing
    • Mixing Glacial Acetic Acid and Methanol is an exothermic: reaction (generates mild heat). While unlikely to self-ignite, mixing large quantities in an enclosed space without ventilation can create a vapor cloud that is easily ignited by a spark. This should always be done in a fume hood