There are two kinds of fires in laboratories: planned and unplanned.
In the 19th century, chemical laboratories and college chemistry buildings were frequently destroyed by fire. Because of the dangers of fire, laboratories and buildings began to be constructed of noncombustible materials both inside and out: metal, brick and stone. By 2017 however, wood and plastic may be found in the laboratory due to the installation of water fire suppression systems installed throughout the laboratory. These protective systems are supplemented by building evacuation alarms activated by heat and smoke and designed to protect human health via early warning of dangerous conditions.
Sprinkler systems are designed to contain fires, and prevent small fires from growing into large fires. In 2015, a laboratory worker spilled a quantity of flammable liquid on the floor. The vapors came into contact with a source of ignition and a large fire began. This activated the fire alarm system and the sprinkler system and the fire was limited to one laboratory. However, the water damage from the sprinkler to expensive scientific equipment and supplies resulted in a loss of $1.6M-$1.9M. There were no injuries to any person.
OSHA and the National Fire Protection Association (NFPA) have created regulations and standards whose goals are to prevent injury, disease and death from hazards including from fire and smoke. NFPA 45 Fire Protection for Laboratories Using Chemicals is one example of a consensus standard that was developed specifically to address fire safety concerns within the lab environment.
Planned vs Unplanned Fires
Planned fires include open flames produced by Bunsen and alcohol burners, flaming soldering torches, welding torches, and burning matches may also be present. Flames are a source of heat, light, smoke and ignition of fuels. Flames however, are not the only source of high heat and ignition. Other sources include: electrical resistance heaters in hot plates or heat guns, ovens, autoclaves, microwave ovens, incandescent lamps, overloaded electrical wires and electrical sparks.
Unfortunately, these are the same sources of unplanned fires!
Therefore, unplanned or “accidental fires” occur when laboratory staff lose control of the materials and equipment they are using to perform an exercise, conduct an experiment or complete a standard procedure.
Fire Safety is therefore a set of procedures intended to prevent and respond to planned and unplanned fires in the laboratory: fire control, fire prevention and fire response.
Laboratory staff must remain constantly aware of the presence, the location and the number of fuel-air-ignition sources in order to prevent unplanned fires.
Fire control procedures are designed to control flames and other sources of ignition to produce the intended result.
Examples of fire safety concerns typically found in the lab environment
Electrical panels, wiring and equipment: 67% of all lab fire are caused by electricity.
Do not overload electrical equipment
Static electrical sparks can ignite flammable liquids and gases
Electrical devices that produce sparks such as motors
Do not use extension cords for permanent wiring
Do not link one power strip to another, (daisy chain)
Do not use plug removal as a substitute for an on-off switch
Do not store flammable or combustible solids or liquids in a standard refrigerator or freezer
Lab made electrical devices must be approved by a competent electrician prior to use.
Do not drape electrical cords over light fixtures or other heat producing equipment.
Remove from service all frayed or damaged electrical cords.
Replace all 3 wire plugs with a missing or damaged grounding prong.
Use sparking tool to ignite fires rather than matches or butane lighters.
Check gas hose connections to ensure they are tight and not leaking. Soap solution is simple to make and use: look for bubbles.
Do not use tygon or plastic tubing to connect burners to gas outlet: use natural rubber hose 3 ft. in length or shorter designed for this use.
Flammable gases and vapors travel distances quickly: avoid producing clouds of vapor that can ignite and flashback to you.
Never leave open flames unattended for any length of time.
Do not use open flame or other high heat source within 6 feet of a container of flammable liquid.
Use open flame in a fume hood whenever possible: remove all flammable and combustible liquids from the fume hood-storage of these liquids as reagents or chemical waste is not allowed.
Flammable and combustible liquids
Flammable liquids readily form vapor clouds which can ignite. This can occur while pouring the liquid or if you spill some liquid onto the bench or floor. Identify all ignition sources before pouring liquids on the open bench, otherwise use the fume hood.
Do not store flammable and combustible liquids in standard refrigerators. The refrigerator must be labelled as explosion proof.
Do not heat flammable liquids in a standard microwave oven: the microwave oven must be labelled as explosion proof.
Fire prevention procedures designed to prevent unplanned fires and reduce the scale of unplanned fires.
Reduce the amount of flammable and combustible liquids outside of flammable liquid storage cabinets.
Do not store flammable and combustible liquids in fume hoods.
Use only small amounts of chemicals.
Limit the size of containers to four liter bottles which can be controlled by one person.
Fire response procedures designed to control unplanned fires and failing that, to prevent injury, disease and death to laboratory staff and others in the building from fire, smoke and other air contaminants produced by the uncontrolled fire.
1. Fire detection and building evacuation alarm
Laboratories are generally equipped with heat detectors and sprinkler heads both of which respond to elevated temperatures (135o F +) produced by fires. Smoke detectors are generally not used because of the high rate of false alarms due to dusts, powders and small planned fires used in laboratories. Activated alarm devices will trigger the building evacuation alarm and require immediate evacuation of the building by all faculty, students, staff and visitors.
Water based sprinkler systems are extremely effective at protecting human life and the building however, sprinkler activation may create collateral water damages to equipment and materials.
2. Once a fire starts there are 3 tools available in the lab to bring fires under control:
Fire extinguishers can be used to put out small (incipient stage) fires. There are four classifications of fire:
A. Burning combustible material such as paper, wood, cloth and plastic.
B. Burning flammable and combustible liquids such as ethanol, acetone and other solvents.
C. Burning electrical equipment that contains flowing electricity.
D. Burning metals such as sodium or magnesium.
The two most common types of extinguishers in the laboratory are the (class) ABC dry chemical and the (class) BC carbon dioxide. Laboratories that store and handle flammable metals must have a Class D powder extinguisher since neither the carbon dioxide or dry chemical extinguisher is effective.
ABC extinguishers use fine powders which are corrosive and difficult to clean. BC carbon dioxide extinguishers use compressed CO2 gas which leaves no residue and no cleaning issues.
Safety showers have handles which can be used to turn on and off the water. A person with burning clothes has three (3) choices: stop, drop, and roll – to smother the fire; deploy a fire blanket to wrap around the burning clothing; or move the victim quickly to a safety shower. Flowing water has the effect of extinguishing the flame as well as cooling the skin and reducing the severity of the burns. Remove burned clothing if possible while in the shower.
Fire blankets are made of treated wool or of inherently non-flammable materials. The blankets have several uses in the laboratory however using a fire blanket to smother burning clothes on a person should be handled very carefully. Use a blanket on a victim only if the blanket is close at hand; otherwise – roll the victim on the floor, or proceed to the safety shower. If a blanket is used to smother flaming clothing, quickly remove the blanket once the flames are extinguished – as a blanket will retain the heat under the blanket and this could lead to more severe burns. Once the flames are extinguished, move the victim to the safety shower immediately to cool the burns. Remove all burned clothing and apply copious amounts of water. Be sure that emergency response notification is immediately activated for fires of any magnitude occurring inside a building (pull the manual fire alarm and call 911).
A fire blanket can also be used for victim modesty after removing burning or contaminated clothing.
Additionally, a fire blanket can be used to cover a flammable liquid spill to prevent ignition of ignitable vapors.