By Kenneth Roy
Posted on 2019-02-27
Most science and STEM laboratories contain chemicals and electrical wiring that could cause smoke or fires. For this reason, the National Fire Protection Association’s NFPA 45 (section 6.3) standard, in accordance with NFPA 10, requires portable fire extinguishers to be installed and maintained in science labs.
The Department of Health and Safety at Tufts University offers the following safety recommendations to prevent electrical fires, open-flame hazards, and fires caused by flammable and combustible liquids.
1. Do not overload electrical equipment.
2. Static electrical sparks can ignite flammable liquids and gases.
3. Electrical devices that produce sparks such as motors.
4. Do not use extension cords for permanent wiring.
5. Do not link one power strip to another (daisy chain).
6. Do not use plug removal as a substitute for an on-off switch.
7. Do not store flammable or combustible solids or liquids in a standard refrigerator or freezer.
8. Lab made electrical devices must be approved by a competent electrician prior to use.
9. Do not drape electrical cords over light fixtures or other heat producing equipment.
10. Remove from service all frayed or damaged electrical cords.
11. Replace all three wire plugs with a missing or damaged grounding prong.
1. Use sparking tool to ignite fires rather than matches or butane lighters.
2. Check gas hose connections to ensure they are tight and not leaking. Soap solution is simple to make and use: Look for bubbles.
3. Do not use Tygon or plastic tubing to connect burners to gas outlet. (Use Bunsen burner flexible tubing designed to meet the American Gas Association’s test standards.)
4. Flammable gases and vapors travel distances quickly; avoid producing clouds of vapor that can ignite and flashback to you.
5. Never leave open flames unattended for any length of time.
6. Do not use open flame or other high heat source within 6 feet of a container of flammable liquid.
7. 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
1. Flammable liquids readily form vapor clouds that 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.
2. Do not store flammable and combustible liquids in standard refrigerators. The refrigerator must be labeled as explosion proof.
3. Do not heat flammable liquids in a standard microwave oven. The microwave oven must be labeled as explosion proof.
Fire prevention strategies
To help prevent unplanned fires, take the following actions:
• Reduce the amount of flammable and combustible liquids outside of flammable liquid storage cabinets.
• Never store flammable and combustible liquids in fume hoods.
• Try to use only small amounts of chemicals for lab activities and demonstrations.
• Containers should be no larger than one gallon.
Fire classification system for laboratories
Laboratories are classified based on the type and amount of flammable gases and flammable and combustible liquids that are stored in the lab. There are four types of laboratories:
• Class A: High fire hazard
• Class B: Moderate fire hazard
• Class C: Low fire hazard
• Class D: Minimal fire hazard
Most laboratories fall under Class A or Class B because they contain varying amounts of flammables and combustible material.
Fire extinguisher classification
Portable fire extinguishers are to be selected and installed based on NFPA 10. Fire extinguishers must comply with area of coverage and travel distance criteria. There are four types of fire extinguishers (A, ABC, BC, and D) designed to combat the following Class A–D fires.
• Type A: ordinary combustibles such as wood, paper, and plastics.
• Type B: flammable liquids such as oils, greases, oil-based paints, and some plastics.
• Type C: electrical equipment such as wires, circuit breaker panels, appliances, and computers.
• Type D: combustible metals such as magnesium, potassium, sodium, and lithium.
According to Fire Extinguisher 101, the best extinguisher for a lab is ABC, a dry chemical unit, which is able to manage A, B, and C fires. Type-D extinguishers, which use dry powder, are recommended as an additional safety measure for handling rare Class-D fires. (Water and dry chemical extinguishers can actually aggravate a Class-D fire.)
Extinguishing the fire
Before you begin working in a lab, first make sure what the institution’s policy is about fighting fires. If a fire breaks out and you have not received approval and training for fighting a lab fire, then you should immediately evacuate the facility and inform the building administration of the fire.
If you decide to fight a fire, consider the following: the size of the fire, evacuation route, and the amount of heat, smoke, and fumes. You should only attempt to extinguish very small fires such those in a beaker or contained in a small area under the fume hood. In this case, students would not need to evacuate the lab. They should just be directed to move away from the area surrounding the small fire. If there are potentially explosive fumes, students should evacuate the lab immediately. Any fire requiring a breathing apparatus should only be addressed by the fire department. In that case immediately evacuate the building. If you are unsure, evacuate the building and call the fire department.
If you are able to contain the fire on your own, secure an ABC or D fire and follow the steps of the PASS acronym:
P: Pull the pin on the extinguisher.
A: Aim the extinguisher low at the base of the flame while keeping a distance of approximately 6 to 10 feet.
S: Squeeze the trigger. The fire extinguisher will run out sometime between 5 to 25 seconds.
S: Sweep from side to side. Try to extinguish the fire in an organized pattern.
Make sure the fire is out. Smoldering fire can burst into flames. Also, after a fire, replace the fire extinguisher as soon as possible. Local fire fighters are dedicated to helping make places safe from fires. They can be of invaluable assistance in training employees and writing standard operating procedures.
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