Section 11: Fire Extinguishers and Fire Safety



Since fire is a common hazard that one faces in a science and engineering laboratory, it is important to be prepared and to know how to deal with a fire emergency. Fire extinguishers are a first line of defense, only if used properly, and under the right conditions. Fire extinguishers are appropriate for small, incipient stage fires, no bigger than a wastepaper basket. University policy states that individuals are not required to fight fires, but those who choose to do so must have been trained in the proper use of fire extinguisher. Training can be arranged by calling the University Chemical Hygiene Officer at 710-2002.




Fire Triangle


Fire Triangle

A fire needs three elements to survive: oxygen, heat and fuel. This is known as the fire triangle. Fires are extinguished by removing one of the three elements of the triangle.















Oxygen Makes up about 21% if the air that we breathe. To sustain a fire, a ratio of 16% oxygen or greater is needed
Fuel Can be combustible or flammable material, and may be solid, a liquid or a gas
Heat Is needed both to initially ignite the fire and also to sustain the fire.




Fire Classifications

Fires are classified based on the type of fuel that is burning.







  • Class A - Wood, paper, cloth, trash and plastics (solid combustible materials that are not metals)
  • Class B - Flammable liquids such as gasoline, oil, kerosene and solvents
  • Class C - Electrical equipment (as long as it's "plugged in" it is considered a Class C fire)
  • Class D - Combustible Metals such as magnesium, potassium and sodium as well as organometallic reagents such as alkyllithiums, Grignards and diethylzine.




Types of Fire Extinguishers


Pressurized Water Fire Extinguisher




Dry Chemical Fire Extinguisher



Carbon Dioxide Fire Extinguisher





  1. Pressurized Water - Class A fire only







    • Water stored under air pressure - 2.5 gallon cylinder
    • Discharge approximately 1 minute, with a range of 10 20 feet
    • If you have a water-filled extinguisher, have it replaced immediately by calling Baylor Facilities


  2. Dry Chemical - Class A, B & C fires








    • Dry chemical powder (ABC - Ammonium phosphate, BC Sodium or potassium bicarbonate) stored under nitrogen pressure
    • Discharge approximately 8 to 15 seconds, with a range of 6-15 feet
    • Extinguishes fire by removing the oxygen through smothering
    • Dry chemical fire extinguishers are suitable for labs, but can cause tremendous mess.
    • Dry chemical powder can infiltrate sensitive electrical equipment and ruin optics, mirrors and other laboratory equipment.


  3. Carbon Dioxide (CO2) - Class B & C fires








    Dry Powder Fire Extinguisher



    • CO2 stored under pressure
    • Discharge approximately 8 to 15 seconds, range 3-5 feet
    • Extinguishes fire by reducing the amount of oxygen around the fire
    • WARNING: CO2 can cause severe chemical burns and freezing of body parts. DO NOT HOLD THE HORN - grip the handle part of the extinguisher
    • WARNING: CO2 can reduce the percent of oxygen in air when in a confined area.
    • Use only in well ventilated areas.


  4. Dry Powder (Sodium Chloride/Sand) - Class D fires






    • This agent can be stored in both extinguishers and storage bins.
    • The agent is applied gently at a sufficient amount to cover the burning metal
    • Extinguishes fires by forming a crust over the burning metal, thus smothering it.





Components of a Fire Extinguisher








  • Cylinder - Holds extinguishing agent and expelling gases
  • Handle - Used to carry and hold extinguisher
  • Trigger - When pressed, releases extinguishing agent through hose and nozzle
  • Nozzle or Horn - Agent expelled through these items
  • Pressure Gauge - Shows pressure of the extinguishing agent being stored in the cylinder. The indicator should be in the green area. CO2 extinguishers do not have a pressure gauge.




Rules for Fighting Fires

The Baylor Police Department should be notified immediately at 2222. If the fire is large or spreading, alert building occupants verbally and activate the fire alarm.












  • You don't know what is burning
  • The fire is spreading rapidly beyond the spot where it started
  • You don't have adequate or appropriate equipment
  • You may inhale toxic smoke
  • Your instincts tell you not to
  • Always position yourself with an exit or means of escape at your back before you attempt to extinguish a fire.
  • If the fire is not out after you have completely discharged the extinguisher, exit the building immediately.




PASS Procedure


PASS Procedure

P ull the Pin - This unlocks the operating lever and allows the agent to discharge from the extinguisher

A im Low - Point the nozzle at the base of the fire

S queeze the Lever - Discharge the agent from the extinguisher. If you release the lever, the discharge stops.

S weep from Side to Side - Move carefully toward the fire, keeping the extinguisher aimed at the base of the fire. Sweep back and forth until the fire is out.







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