CHEM 421 Safety Presentation

Hazard Symbols You Must Know

Take Electricity Seriously Over 30,000 non-fatal shocks occur each year. Over 30,000 non-fatal shocks occur each year. Over 600 deaths occur annually due to electrocution. Over 600 deaths occur annually due to electrocution. Source: Bureau of Labor Statistics

Electrical Accidents Leading Causes of Electrical Accidents: Leading Causes of Electrical Accidents: – Drilling and cutting through cables – Using defective tools, cables and equipment – Failure to maintain clearance distance of 10 feet – Failure to de-energize circuits and follow Lockout/Tagout procedures – Failure to guard live parts from accidental worker contact – Unqualified employees working with electricity – Improper installation/use of temporary electrical systems and equipment – By-passing electrical protective devices – Not using GFCI (ground fault circuit interrupters) devices – Missing ground prongs on extension cords

Hazards of Electricity Shock – Most common and can cause electrocution or muscle contraction leading to secondary injury which includes falls Shock – Most common and can cause electrocution or muscle contraction leading to secondary injury which includes falls Fires – Enough heat or sparks can ignite combustible materials Fires – Enough heat or sparks can ignite combustible materials Explosions – Electrical spark can ignite vapors in the air Explosions – Electrical spark can ignite vapors in the air Arc Flash can cause burns ranging from 14,000 °F to 35,000 °F Arc Flash - can cause burns ranging from 14,000 °F to 35,000 °F Arc Blast In a short circuit event copper can expand 67,000 times. The expansion causes a pressure wave. Air also expands, adding to the pressure wave. Arc Blast – In a short circuit event copper can expand 67,000 times. The expansion causes a pressure wave. Air also expands, adding to the pressure wave.

Fundamentals of Electricity Electrical current is the flow of electrons through a conductor. Electrical current is the flow of electrons through a conductor. A conductor is a material that allows electrons (current) to flow through it. A conductor is a material that allows electrons (current) to flow through it. An insulator resists the flow of electrons. An insulator resists the flow of electrons. Resistance opposes electron flow. Resistance opposes electron flow.

How Shocks Occur Current travels in closed circuits through conductors (water, metal). Current travels in closed circuits through conductors (water, metal). Shock occurs when the human body becomes a part of the circuit. Shock occurs when the human body becomes a part of the circuit. Current enters at one point & leaves at another. Current enters at one point & leaves at another.

Severity of the Shock Severity of the Shock depends on: – Amount of current Determined by voltage and resistance to flow Determined by voltage and resistance to flow – Path through the body – Duration of flow through the body – Other factors such as general health and individual differences

Effects of Current Flow More than 3 milliamps (ma): painful shock More than 3 milliamps (ma): painful shock More than 10 ma: muscle contraction More than 10 ma: muscle contraction More than 20 ma: considered severe shock More than 20 ma: considered severe shock More than 30 ma: lung paralysis - usually temporary More than 30 ma: lung paralysis - usually temporary More than 50 ma: possible ventricular fibrillation (usually fatal) More than 50 ma: possible ventricular fibrillation (usually fatal) 100 ma to 4 amps: certain ventricular fibrillation (fatal) 100 ma to 4 amps: certain ventricular fibrillation (fatal) Over 4 amps: heart paralysis; severe burns Over 4 amps: heart paralysis; severe burns

Electrical Isolation We can be safe by keeping electricity away from us. We can: We can be safe by keeping electricity away from us. We can: – Insulate the conductors Example: The insulation on extension cords Example: The insulation on extension cords – Elevate the conductors Example: Overhead powerlines Example: Overhead powerlines – Guard the conductors by enclosing them Example: Receptacle covers, boxes, & conduit Example: Receptacle covers, boxes, & conduit

Insulating the Conductors The first way to safeguard workers from electrically energized wires is through insulation. The first way to safeguard workers from electrically energized wires is through insulation. Rubber and plastic is put on wires to prevent shock, fires, short circuits and for strain relief. Rubber and plastic is put on wires to prevent shock, fires, short circuits and for strain relief. It is always necessary to check the insulation on equipment and cords before plugging them in. It is always necessary to check the insulation on equipment and cords before plugging them in. Remember, even the smallest defect will allow leakage! Remember, even the smallest defect will allow leakage! Insulated (but not grounded) Insulated (also grounded – see third pin)

Defective Extension Cords Photos depict hazardous condition Throw this away and buy a new one! Don’t use it!

Guarding the Conductors Another way we safeguard workers from electrically energized wires is by guarding them. Another way we safeguard workers from electrically energized wires is by guarding them. Covers, boxes, and enclosures are often put around conductors to prevent worker contact. Covers, boxes, and enclosures are often put around conductors to prevent worker contact. It is always necessary to check that electrical boxes and panels are covered and free from missing “knock-outs.” It is always necessary to check that electrical boxes and panels are covered and free from missing “knock-outs.” Remember, electric equipment operating at 50 volts or more must be guarded! Remember, electric equipment operating at 50 volts or more must be guarded! Photo depicts hazardous condition No knock- outs!

Guarding the Conductors Photos depict hazardous condition Don’t use either one of these!!

Guarding the Conductors Photos depict hazardous condition Yikes! Put a cover on this!

Equipment Grounding We can be safe by providing a separate, low resistance pathway for electricity when it does not follow normal flow (ground prong/pin). We can be safe by providing a separate, low resistance pathway for electricity when it does not follow normal flow (ground prong/pin). Grounding gives the stray current somewhere to go and keeps your body from becoming part of the circuit. Grounding gives the stray current somewhere to go and keeps your body from becoming part of the circuit. Use non-conducting (wood, plastic) supports when using power tools

Defective cord incident with metal support Worker attempted to climb scaffold with electric drillWorker attempted to climb scaffold with electric drill Drill was used, even though the cord was damaged with bare wires showingDrill was used, even though the cord was damaged with bare wires showing The bare wire contacted the metal scaffoldingThe bare wire contacted the metal scaffolding The worker was electrocutedThe worker was electrocuted Depicts hazardous condition

Can You Rely on Grounding? Grounding will not work if the electricity can flow through you more easily than the ground. You become the path of least resistance = electrocution Grounding will not work if the electricity can flow through you more easily than the ground. You become the path of least resistance = electrocution This can happen when: This can happen when: – Your tool doesn’t have a ground pin. – You are working in wet locations. – You are touching a metal object. Pay attention to your surroundings when you use grounded portable tools

What Must be Grounded? All circuits and extension cords All circuits and extension cords All noncurrent carrying metal parts All noncurrent carrying metal parts Portable & semi-portable tools and equipment unless double insulated Portable & semi-portable tools and equipment unless double insulated A plug with a ground pin (good!)

Do not use a cord or tool if the ground pin has been removed You will become the path of least resistance for current = electrocution Photos depict hazardous condition Don’t Use This!

Do Not Reverse Polarity or use a cord/tool with reversed polarity The prongs are different sized so you can not turn the plug around. If you do, the electrical fields are always energized. If there is moisture present, the case is likely to be “hot”. Even with double-insulated tools, you still could get a shock. Photo depicts hazardous condition Don’t use this!

Circuit Interruption We can be safer by automatically shutting off the flow of electricity in the event of leakage, overload, or short circuit. We can be safer by automatically shutting off the flow of electricity in the event of leakage, overload, or short circuit. Ground Fault Circuit Interrupters (GFCI) are circuit protection (or “overcurrent”) devices that protect you, the worker. Ground Fault Circuit Interrupters (GFCI) are circuit protection (or “overcurrent”) devices that protect you, the worker. Circuit breakers & fuses protect equipment, not you, because they take too much current & too much time to trip. GFCI protects you. Circuit breakers & fuses protect equipment, not you, because they take too much current & too much time to trip. GFCI protects you. GFCI outlets have the reset buttons.

Temporary Wiring There must be separate circuits for electric tools and lighting, each labeled as such. There must be separate circuits for electric tools and lighting, each labeled as such. Light circuits do not require a GFCI. Light circuits do not require a GFCI. – Unless used in a wet location. Test branch circuits before use Test branch circuits before use Maintain vertical clearances Maintain vertical clearances Insulate wires from their supports Insulate wires from their supports Cords must be draped overhead to protect you and your labmates Wrong place for cord

Extension Cords and Cables Must be in good shape without splices Must be in good shape without splices Cannot be secured with staples, nails or bare wire Cannot be secured with staples, nails or bare wire Must be protected from damage Must be protected from damage Must have a ground pin Must have a ground pin Should be inspected regularly and pulled from service if defective Should be inspected regularly and pulled from service if defective Cannot be repaired with electrical or duct tape Must repair with heat-shrink sleeve or bonding/vulcanizing tape to retain original insulation properties Cannot be repaired with electrical or duct tape Must repair with heat-shrink sleeve or bonding/vulcanizing tape to retain original insulation properties SUBPART Photos depict hazardous condition Bad idea!

Photo depicts hazardous condition Yikes!

Safe Work Practices De-energized circuits and equipment must be locked/tagged out. De-energized circuits and equipment must be locked/tagged out. If you are working on a circuit with a fuse, lock the fuse box while you work – or, someone could come and flip the switch back on while you’re working. Lock the box for your protection

Safe Work Practices No metal supports or ladders used during or near electrical work. No metal supports or ladders used during or near electrical work. No wet hands when plugging or unplugging cords/equipment. No wet hands when plugging or unplugging cords/equipment. No raising or lowering tools by the cord. No raising or lowering tools by the cord. Unless equipment is designed for it, do not use electrical tools or equipment in damp and wet locations. Unless equipment is designed for it, do not use electrical tools or equipment in damp and wet locations. 53 K SUBPART Photo depicts hazardouscondition Getting through this person to the ladder is now the path of least resistance for the current = electrocution Bad idea!

Summary – Hazards & Protections Hazards Inadequate wiring Inadequate wiring Exposed electrical parts Exposed electrical parts Wires with bad insulation Wires with bad insulation Ungrounded electrical systems and tools Ungrounded electrical systems and tools Overloaded circuits Overloaded circuits Damaged power tools and equipment Damaged power tools and equipment Using the wrong PPE and tools Using the wrong PPE and tools Overhead power lines Overhead power lines All hazards are made worse in wet conditions All hazards are made worse in wet conditions Using damaged extension cords Using damaged extension cords Unqualified workers doing electrical work Unqualified workers doing electrical work 55 K SUBPART Protective Measures Proper grounding Proper grounding Use GFCI’s Use GFCI’s Use fuses and circuit breakers Use fuses and circuit breakers Guard live parts Guard live parts Lockout/Tagout Lockout/Tagout Proper use of flexible cords Proper use of flexible cords Close electrical panels by Competent Person Close electrical panels by Competent Person Employee training Employee training Ensure competent person on site Ensure competent person on site Use proper approved electrical equipment Use proper approved electrical equipment Have qualified person install electrical devices Have qualified person install electrical devices

Report any concerns If you have any safety concerns about the lab you are working in or the people working around you, you can contact: – Your lab instructor – Dr. Brooke Van Horn– Head of the departmental safety committee – Dr. Pamela Riggs-Gelasco – Department Chair for Chemistry and Biochemistry – Dr. Jim Deavor, Associate Dean of the School of Science and Mathematics.