Fire and electrical hazards

 

FIRE HAZARD

Laboratories using solvents in any quantity have a very high potential for flash fires, explosion, rapid spread of fire, and high toxicity of products of combustion (heat, smoke, and flame).

For combustion to occur the following conditions are needed (fire tetrahedron): presence of oxygen, presence of heat to attain ignition temperature (heat), combustible material (fuel) and chemical reactions. Fire extinguishers put out fire by talking one or more elements.

Classes of fire

There are six different types of fire classes and here is a detailed list covering types of fire included in each class:

Type	Causes
Class A	Fires caused by combustible materials including paper, fabric, wood and other flammable solids.
Class B	Fires caused by flammable liquids such as paint, turpentine or petrol among others.
Class C	Fires caused by flammable gases including methane, butane or hydrogen among others.
Class D	Fires caused by combustible metals including potassium, aluminum or magnesium among others
Class F	Fires include those caused by cooking oils such as a chip-pan fire
Electrical Fires	Fires involving electrical equipment but upon removal of the electrical item, the fire class is changed.

 

Preventive measures

·         Proper storage of chemicals: flammable liquids are kept at a minimum, and stored in flammable liquid storage cabinets. Never allow more than ten gallons of liquid to be outside of cabinets at any time. Store compressed gases with valve caps on when not in use, and keep cylinders firmly anchored in place. For incompatible substances, store in separate areas e.g. keep oxidizers well away from flammable liquids and gases. Do not store flammable liquids in fume hoods.

·         Proper planning of work

·         Keep the working areas uncluttered, clean and minimal obstructions.

·         Wear Personal Protective Equipment

·         Use of barriers in place: shields, hood doors

·         Develop an emergency plan that notifies the people what to do and where to get things such as fire extinguishers, emergency shower. Also, provide training on this plan.

 

Fire procedures

1.0    Notify the other occupants of the immediate space, those from a far using fire alarm and emergency responders

2.0    Evacuate people in the immediate area of the problem, space within which the problem has occurred and the building within which the space is located.

3.0    Isolate by lowering hood sash, close lab door(s), close corridor doors.

4.0    Extinguish the fire it is safe to do so.

 

 

Study Question

 

List the different types of fire extinguishers.

 

 

ELECTRICAL HAZARD

Most of the equipment in the laboratory is powered by electricity. If mishandled and not maintained properly, it increases the chances of being an electrical hazard.

The major hazards associated with fire are electrical shocks and fire (when electricity is the source of ignition  for flammable chemical gas or reagent).

 

Electrical shocks

 

·         Occur when the body becomes part of the electric circuit, either when an individual comes in contact with both wires of an electrical circuit, one wire of an energized circuit and the ground, or a metallic part that has become energized by contact with an electrical conductor.

·         The severity and effects of an electrical shock depend on a number of factors, such as the pathway through the body, the amount of current, the length of time of the exposure, and whether the skin is wet or dry.

·         Water is a great conductor of electricity, allowing current to flow more easily in wet conditions and through wet skin.

·         The effect of the shock may range from a slight tingle to severe burns to cardiac arrest.

 

 

Fire

·         Sparks from electrical equipment can serve as an ignition source for flammable or explosive vapors or combustible materials. 

 

Precautions to reduce electrical hazards

·         Proper insulation of wires to prevent direct contact of wires.

·         Guarding of parts of electric equipment operating at 50 volts or more (i.e., electrophoresis devices) to protect against accidental contact.

·         Only use equipment with three-prong plugs providing a path to ground for internal electrical short circuits, thereby protecting the user from a potential electrical shock.

·         Use of circuit protection devices designed to automatically limit or shut off the flow of electricity in the event of a ground-fault, overload or short circuit in the wiring system. Ground-fault circuit interrupters, circuit breakers and fuses are three well-known examples of such devices. Fuses and circuit breakers prevent over-heating of wires and components that might otherwise create fire hazards. They disconnect the circuit when it becomes overloaded. This overload protection is very useful for equipment that is left on for extended periods of time, such as stirrers, vacuum pumps, drying ovens and other electrical equipment.

·         Inspect wiring of equipment before each use. Replace damaged or frayed electrical cords immediately.

·         Use safe work practices every time electrical equipment is used such as:

 

Ø  Avoid contact with energized electrical circuits.

Ø  Use guarding around exposed circuits and sources of live electricity.

Ø  Disconnect the power source before servicing or repairing electrical equipment.

Ø  When it is necessary to handle equipment that is plugged in, be sure hands are dry and, when possible, wear nonconductive gloves and shoes with insulated soles.

Ø  If it is safe to do so, work with only one hand, keeping the other hand at your side or in your pocket, away from all conductive material. This precaution reduces the likelihood of accidents that result in current passing through the chest cavity.

Ø  Minimize the use of electrical equipment in cold rooms or other areas where condensation is likely. If equipment must be used in such areas, mount the equipment on a wall or vertical panel.

Ø  If water or a chemical is spilled onto equipment, shut off power at the main switch or circuit breaker and unplug the equipment.

Ø  If an individual comes in contact with a live electrical conductor, do not touch the equipment, cord or person. Disconnect the power source from the circuit breaker or pull out the plug using a leather belt.

 

·         Know the location and how to operate shut-off switches and/or circuit breaker panels. Use these devices to shut off equipment in the event of a fire or electrocution.

·         Limit the use of extension cords. Use only for temporary operations and then only for short periods of time. In all other cases, request installation of a new electrical outlet.

·         Multi-plug adapters must have circuit breakers or fuses.

·         Place exposed electrical conductors (such as those sometimes used with electrophoresis devices) behind shields.

·         Minimize the potential for water or chemical spills on or near electrical equipment.

 

Quick Question:

Highlight FIVE symptoms shown by a person affected by electric shock.

 

 

APPENDIX

 Types of fire extinguishers

Type	Characteristics
Foam extinguishers	Most common type Water based extinguishers Works for class A fire Label color is cream Not be used for fires caused by flammable metals, kitchen fires and fires Work by creating a cooling effect on the fuel that is responsible for causing the fire. When it is poured on burning liquid, the fire is extinguished by creating a barrier between the fuel and the flame with the help of the foaming agent.
Water extinguishers	Class A fire risk Bright red label This type of extinguisher is equipped with a spray nozzle instead of a jet nozzle which provides a greater surface area to quickly put out fire. Works by creating a cooling effect on the liquid that causes the burning fuel to burn at a slower rate until the flames are completely extinguished.
Dry powder extinguishers / ABC extinguishers	Used for class A, class B and class C fires.   Should not be used in enclosed spaces as the dry powder in the extinguisher can be easily inhaled and it’s not easy to clean up the leftover residue once the fire is over.   These can also be used for fires involving electrical equipment and caused by flammable metals. However, it should not be used for fires that involve electrical equipment over 1000 V and fires that involve cooking oil. There are special dry powder extinguishers used only on flammable metals such as magnesium and titanium.   The label color for this type of extinguisher is blue.   This type of fire extinguisher may be used for fires caused by various organic materials including wood, coal, textiles, fabrics, cardboard and paper among others, flammable liquids including petrol and paint as well as flammable gases including acetylene and liquid petroleum gas.                                                                                                                                             Mechanism: smother fires by forming a barrier between the fuel and source of oxygen.
Wet chemical	Designed for use on Class F fires, involving cooking oils and fats (Class F) and Class A fires.   The label color for this type of extinguisher is yellow.   Wet chemical extinguishers can also be used for fires caused by various organic materials including wood, coal, textiles, fabrics, cardboard and paper.
Carbon IV oxide extinguishers	Mainly used for electrical fire risks and are usually the main fire extinguisher type provided in computer server rooms. They also put out Class B fires. CO2 extinguishers suffocate fires by displacing the oxygen the fire needs to burn. This type of extinguisher has a black label.