What Are The Safety Measures When Using Electricity
10 Electrical Safety Rules

  • Prevent electrical equipment from contacting wet areas.
  • Ensure safe use when unplugging.
  • Install properly and tidy electrical cords.
  • Understand your switchboard.
  • Look out for electrical lines.
  • Childproof your outlets.
  • Investigate Flickering Lights.
  • Install warning signs.

Meer items

What are the safety measures of using electricity?

6. Keep electrical devices and outlets away from water to prevent shock. – Water and electricity don’t mix well. To follow electrical safety rules, keep electrical equipment dry and away from water prevents damage to appliances and can protect against personal injury and electrocution.

What are the 3 safety devices in electricity?

Figure 1: A fuse box in a basement is one type of electrical safety device. Many of the energy services around the house use electricity. It is extremely important to have various safety devices to protect from fire and electrocution. Industrial electricity use has similar problems.

What is an example of an electrical safety checklist?

Are there any cables or wires without proper casing, found in the factory? Are any electrical wires improperly spliced or taped? Is electrical equipment properly grounded to prevent electrocution or fire? Are any electrical wires found in damp areas or standing water?

What are the hazards of electricity?

The main electrical hazards – The main hazards of working with electricity are:

electric shock and burns from contact with live parts injury from exposure to arcing (when electricity jumps from one circuit to another) fire from faulty electrical equipment or installations explosion caused by unsuitable electrical apparatus static electricity igniting flammable vapours or dusts, for example in a spray-paint booth

Electric shocks can also lead to other types of injury, for example by causing a fall when working from ladders or scaffolds etc. Even incorrectly wiring a plug can be dangerous and lead to fatal accidents or fires.

How will you protect yourself and your body while doing electrical works?

4. Use Personal Protective Equipment (PPE) – It’s there for a reason. PPE aims to protect workers against health and safety risks posed by their work environments. PPE is designed as the last ‘stage’ of protection, but is imperative nonetheless. Insulated gloves, fire resistant clothing and face shields should be worn when working on energized electrical equipment.

What are 5 simple safety devices?

By Michael Panish, Construction Expert Witness – As a construction expert witness, I am often asked about the importance of using safety equipment. I have many years of personal experiences with the proper observance of safety procedures and appropriate safety equipment requirements.

  1. In my professional life as a general building contractor, I have conducted regularly scheduled safety meetings, provided safety equipment to my employees, and trained my workmen on the proper ways to protect themselves while on the job.
  2. I have personally monitored my crews to verify that appropriate protective gear is worn and used at all times when needed.

In my personal life, safety and appropriate protective equipment is equally as important. I own, maintain, and use just about every piece of job specific safety equipment that is available. It is my opinion that your home workshop, personal residence, and yard can become just as dangerous as a construction jobsite when work is being performed.

  • Many homeowners think that work around the house is not the same as work on a construction jobsite.
  • Do-it-yourself television programs make renovations seem simple and easy to accomplish.
  • As a result of these numerous television shows, some homeowners attempt to tackle a renovation project completely unprepared, at least with regard to the usage of safety equipment.

I have watched many television programs where the contractors, workmen, and homeowners operate noisy power tools without hearing protection. They tear apart walls and demolish interior partitions without dust masks, gloves, or face protection. While performing hazardous work, these tradesmen do not always address job safety or the potential health hazards from asbestos related products, plaster dust, or mold issues that may exist within the scope of the home renovation work.

These television shows can mislead or ignore the fact that the general public may view these projects as safe and easy to accomplish. They potentially create safety concerns that can affect the novice and uninformed viewer. Serious personal injuries occur frequently to homeowners doing simple weekend yard work, mainly due to the fact that they failed to wear protective garments, eye or hearing protection.

The “weekend warrior” risks potential injury by over-reaching while working on undersized or improperly positioned ladders, filling hot tools with explosive gasoline, or digging trenches without checking for underground utilities. They purchase power tools that they may not know how to use and lack the understanding of the potential harm that the tool can create.

In many states, it is a requirement that a construction or demolition site be surveyed for hazardous materials such as asbestos or petroleum products prior to beginning any work. Even some professional contractors ignore this investigation and most homeowners are completely unaware of this necessary safety check.

The importance of this preliminary site survey cannot be overstated. Contamination from construction debris or hazardous waste is not only dangerous to the site workers, but can seriously affect the environment and can create costly cleanup related fees.

  1. I have been the retained construction expert on several personal injury cases that involved trained construction workers.
  2. These workmen are required to wear and use protective clothing such as steel toed shoes and a hard hat during normal on the job hours.
  3. However, when working on their own personal residences, they chose to wear casual clothes such as tennis shoes, and baseball hats, all the while drinking alcohol.

The lack of proper protective gear, in combination with alcohol consumption, and numerous distractions ended in serious personal injuries. In one of my past construction injury cases, an inebriated tradesman/homeowner decided to adjust an overhead sectional garage door spring.

He had no training of any type dealing with these springs and paid no attention to the installed spring tension warning labels. What made him feel qualified was that he had watched a couple of garage door installer’s repair or adjust a neighbors’ garage door. Not understanding the tremendous stored energy in the garage door torsion spring, and after having had a few drinks, the homeowner decided he had the courage to remove the bolts that secure the spring and make an adjustment.

He chose to use a small wrench. The short tool that he used became unmanageable in his hand, he lost his grip and the tool which was now powered by the force of the stored energy in the spring, flew off of the bolts and smashed into his face and head.

How does this story relate to safety products? Safety and the appropriate usage of safety products start with the conscious decision on the part of the user to employ those safety devices. Rational behavior and common sense are often impaired by the usage of alcohol, and any construction or yard work should not be performed while under the influence.

Safety products for almost every purpose are available at most local home centers. While the quality and durability of these products may or may not equal products in professional trade supply houses, they at least begin to address the importance of using appropriate safety products to keep the homeowner aware that safety concerns are real.

In addition, most safety products are currently available on line and can be purchased for next day delivery. Inform Others to Leave You Alone While You Are Working One of the most basic forms of safety for any jobsite or home location is to make sure that you have a clear and secure work area. Inform co-workers or your family to leave you alone to do your work.

Do not play games around your work space or allow children or animals to distract you or divert your attention in any way. A quick glance toward a diversion can create enough distraction to create severe personal injuries. Whether you are using a portable saw, table or hand saw, distractions equal danger.

  1. Pay strict attention to your work, stop when you become tired or lose interest, and remain focused on your project without any outside interruptions.
  2. This aspect of safety does not require purchasing any piece of equipment.
  3. Continual and ongoing safety should always be your first priority.
  4. What Safety Devices Should a Homeowner Have in Their Home? The following list is a suggested start to basic equipment you should have around the house.

Fire Extinguishers Many common fires around the house can be stopped with the usage of a proper fire extinguisher. While quick action and correct usage may put out the fire, it is important to also be aware of the limitations of the extinguisher used.

  • Fully understand and read all included instructions prior to usage.
  • It is a good and safe practice to regularly inspect your extinguisher to verify that it is properly charged.
  • It is also a good idea to make sure that the contents of the extinguisher do not become a solid mass.
  • A few times a year it is recommended that the contents be shaken.

Alternatively, a rubber mallet can be used to smack the bottom of the device (do not hit the valve or hose components). This agitation will help to prevent the solid materials from clumping into an unusable mass. Smoke, Fire, Carbon Monoxide Detectors These devices give advance warning to unseen, unknown, or undetectable dangerous conditions.

  • It is important to check the condition of the power source to these detectors.
  • If they are hardwired into the building, check to verify that a battery back-up exists.
  • If the type of battery installed charges during normal conditions it probably does not need replacing every six months.
  • If the battery is expendable, it is good practice to change it whenever daylight savings events occur.

It is good practice to test these devices, either hard wired or battery type, at least once a month to verify that they are working correctly. If a test fails, replace the device immediately to assure your protection. Seek additional information regarding these devices from the manufacturer or online sources.

Fire Escape Ladders Add extra safety to your family if you have multiple floors. Stairwells can often become chimneys, depending upon the location of a fire. In the event of a fire, it is important to have multiple egress points. Pre-boxed fire escape ladders can be kept under windows, beds or adjacent closets to be used in the event of a fire.

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Always check the condition of the ladder immediately after purchase to assure that the ladder is usable in the event of an emergency situation. These ladders are available in some home centers and online for immediate shipping. Dust Masks & Respirators Respirators and dust masks are an important part of many jobs.

  1. It is important to make sure that your lungs and airways are protected from adverse chemicals and airborne contaminants.
  2. There are many types of dust masks available.
  3. Dust masks should not be confused or interchanged with respirators.
  4. A dust mask is generally a low cost paper or synthetic filtering device manufactured to help stop dust, debris, and dirt from entering your nose and mouth.

A respirator is generally considered a cartridge and filtered system to trap contaminants and purify the air particles prior to entering your respiratory system. Make certain that the usage of the proper type of mask or respirator is proven for the type of work that you are performing.

Make certain that the filters and cartridges in a respirator are approved by NIOSH or OSHA and meet the requirements to protect you. An indication that a respirator needs the replacement of filters is when you begin to smell or taste the products you are using the respirator to filter. When that occurs, always stop work, replace the cartridge or filter prior to continuing.

Always read, follow, and understand the instructions that come with this piece of safety equipment. Check with the manufacturer or supplier to verify that you are using appropriate products for your job. More professional and stringent requirements for the usage of certain type of respirators include medical evaluations prior to the issuance of the respirator.

  • An example of this type of requirement would pertain to work related to asbestos or mold abatement.
  • In addition to proper training prior to working with asbestos, it is important that a medical evaluation determines that your body is able to properly function while you are wearing the approved respirator.

The removal of asbestos or mold is not to be taken lightly and should not be performed by an untrained, unlicensed or uncertified contractor. This is not a project for a homeowner. Gloves Gloves for all purposes (Rubber, latex, chemical resistant, electrical insulated, leather work, thermal insulated, heat resistant, Kevlar reinforced, etc.) – Gloves are a very basic and easy to find safety item.

  1. The importance of proper protection of your hands and arms cannot be overstated.
  2. There are as many types of gloves available as there are types of jobs.
  3. It is important to know the limitations and requirements of your gloves prior to beginning work.
  4. Hearing Protection Hearing protection includes equipment such as ear plugs and head phones.

Long term hearing loss can be created by a sudden unexpected loud noise. It is important to plan for that possibility and provide adequate hearing protection. Long term exposure to low levels of certain frequencies can also damage hearing. Consult online guides, job related service manuals, and other available sources to determine the correct type of hearing protection that should be used for any job.

  1. Repeated exposure to yard and lawn equipment can be very damaging to your ears, and even though it may occur on an infrequent basis, it is important for anyone exposed to these products to protect their ears.
  2. Safety Clothing Safety clothing for specialized usage.
  3. Some examples of protective clothing products and related items include Kevlar chainsaw protective chaps, gloves, boots, hard hat with face shield, etc.

Chain saw users can encounter several assaults on their bodies at every usage. Hearing can be seriously affected, so headphones are essential. A hardhat is recommended to protect against the inadvertent tree branch falling from above. A face shield is suggested to protect against flying wood chips, tree limbs, and branches that may brush past a user.

Safety glasses are suggested to protect against sudden projectile impacts that pass the face shield. One of the most significant and potentially lifesaving products that can be worn are products made using Kevlar fabric. This fabric, when cut with an errant chain saw chain, becomes shredded and grabs the chain, hopefully stopping the chain before cutting your body parts.

It is important to wear protective boots, chaps, gloves, and vests made with Kevlar at all times during usage of a chain saw to protect all major body parts and extremities. Work Shop / Wood Shop Protection Face masks, goggles, dust masks, respirators, hearing protection, proper gloves for specific tasks, ventilation devices for airflow, and dust collectors are recommended.

  1. Understand the task that you are planning, and make certain to have all needed safety products and equipment prior to starting your project.
  2. A good first aid kit is important to have in your workshop.
  3. Boots Steel Toed Work Boots or Regular Work Boots are essential for working with heavy objects that can fall on your feet.

Steel toed boots have a protective reinforcement in the toe to protect your foot from falling objects, compression, or punctures. For light products, non-steel toed shoes may be sufficient. The addition of steel in your work boots is good additional insurance against foot injuries.

Steel toed shoes are often professional requirements on most work sites. Why not add the protection of steel toed work boots when you plan to buy your next pair of work shoes? Ladders Proper and appropriate ladders for multipurpose use. Never use a ladder for more than its’ intended purpose. Fiberglass ladders offer non conductivity from electrical sources, come in a variety of types and load ratings, and last for years.

In most cases, they are far more durable than a wooden ladder or any aluminum ladder product. They may cost a little more, but are well worth the price in the long run, and will provide many years of safe usage if properly maintained and stored. Ground Fault Circuit Protection Ground fault circuit protectors for electrical outlets in water or moisture adjacent areas.

  • While a G.F.I.
  • Ground fault interrupter) is an electrical code requirement in wet locations in newer construction, older homes may not have been upgraded to include these devices.
  • Homeowners, not thinking about shock hazards, may not know if the outlet that they are connecting exterior extension cords to are grounded or protected by a G.F.C.I.

(Ground fault circuit interrupter.) Unprotected circuits and outlets now connected to these electrical extension cords can lead to shock hazards or even death. The above list of suggested safety equipment is not to be considered an exhaustive resource of information.

  1. Suggestions made in this article should offer some assistance in determining the type of products that will help to increase your safety when working around your home.
  2. The author is not responsible for any omitted or included content and urges the reader to make informed decisions and take personal responsibility to assure that they have received all the information to make informed decisions for any project.

The author is not responsible for any manufacturers’ products, defects, or usage of those products. Be informed that readers of this article assume all risks associated with using safety equipment mentioned in the article. Remember to purchase the best quality safety products that you can find.

Remember the saying: If you have a ten dollar head, get a ten dollar helmet. The same adage applies to all safety gear. Buy the best products available, check what a tool or equipment supplier recommends, and research the proper way to use the safety equipment. If you are unsure as to whether something is safe, and you have any doubts, do not proceed with any work.

Seek professional assistance and protect yourself from possible severe bodily injuries. Sample Injuries that can occur around the Home: Chain Saw related injuries in many areas around the country, it is not unusual for a homeowner to own and routinely use a chain saw.

From information given to me at many chain saw supply stores, very few people choose to purchase the protective garments such as Kevlar lined gloves, boots and chaps. And, they don’t always concern themselves with eye, ear, or head protection. When I purchased a chain saw several years ago, the local store owner was surprised and pleased that I requested and purchased all of the safety products that pertained to usage of that saw.

The usual homeowner attitude is that “I am not working professionally, so my casual usage of this chain saw will not be a problem.” With all accidents, it only takes one incident to change your life completely. The chain saw itself is only one part of a potential serious injury.

  1. Falling tree branches can strike you on the head, scratch your face, and injure your eyes.
  2. Loud noise from the chain saw is also significant in damaging your ears and creating fatigue while working for long periods of time.
  3. Wearing proper Kevlar protective clothing can save your life.
  4. The steel like threads that make up Kevlar become entangled in a chain saw chain stopping its’ cutting action instead of allowing the chain to cut a vital body part such as arteries in your leg, arm or hand.

Kevlar reinforced steel toed work boots also help protect your feet from heavy objects and accidental contact with your chain saw blade. Work shop related injuries Many homeowners enjoy the time spent in their workshops in out-buildings, garages, and basements.

Workshop injuries occur for many reasons. Working without protective clothing or eye and ear protection top the list. Working for too long, becoming tired, and attempting to finish a project often create careless mistakes that lead to life altering injuries. Over working tools (pushing the tools to perform tasks that they are not designed to do or the over-stressing of blades and drill bits) lead to fracturing and projectile ejection.

Quality safety equipment can help to limit the potential injuries from unpredictable occurrences. But, most importantly, common sense and knowing when to stop work are the most important aspect in preventing personal injury. Fresh air is also essential to assure your safety.

  1. Make sure your work space is properly ventilated and there is adequate air exchange.
  2. Never spray paint or other finishes in an enclosed space.
  3. In addition to becoming difficult to breathe and see, sprays can become explosive if the right conditions and airborne concentrations exist.
  4. Summary The purpose of wearing protective products should make perfect sense to everyone.

It is important that you, as the power tool user, take it upon yourself to purchase and use appropriate safety equipment. Many big box stores gladly sell potentially dangerous power tools to anyone. Normally, there is not any verification to see if the new power tool buyer has proper training, safety equipment or enough information to use the tool safely.

While there is no law regarding regulating the purchase of most dangerous tools, even a simple hammer can create bodily injury if not used properly. It is not the responsibility of a store to enforce the usage of safety equipment, but it seems that it would be a good policy to inquire with the new tool buyer whether or not they are prepared to safely use their new tool and have proper safety equipment.

Major life threatening injuries can result from the improper usage of power tools and even small hand tools. It is important to remember to use any necessary safety equipment that would protect you from injury while using a specific piece of equipment.

Personal safety is the responsibility of the individual. Safety information and products are available online and in trade publications and journals that offer construction related products. Mike has been designated by Plaintiff and Defense as construction expert witness in jobsite injury and accident cases resulting from improper or unsafe tool usage, inappropriate safety precautions, and hazardous working conditions.

He has been called upon by insurance adjusters and claims representatives to evaluate the jobsite conditions and assist them in determining the reason for the claim or injury. In addition, insurance claims adjusters have called upon him to help them analyze the causation of fires and floods that have resulted from incorrect usage or mishandled tools and equipment.

Mike has been an invaluable part of the team representing the Plaintiff when a claim of unsafe and reckless behavior on the part of the employer was determined. He has provided his expert services in defense of claims that have limited the Defendant’s liability in other cases. His past experience in the trades has allowed his evaluations to carry significant weight during mediations and arbitration hearings.

The vast majority of cases where he was the retained construction expert have settled favorably for his clients. A full list of Mike Panish’s construction expert witness services is available on his website at www.ConstructionWitness.com.

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Why are electrical safety devices important?

Why Is Electrical Safety Important? You cannot smell, hear, or see electricity, so making sure you have the right systems in place to manage this hazardous energy is critical to the wellbeing of your employees and your Company. There are two major hazards of electricity: Electrical safety is important because hazards such as arc flash and shock can result in death if you are exposed to them.

Cardiac arrest due to the electrical effect on the heart Muscle, nerve, and tissue destruction from a current passing through the body Thermal burns from contact with the electrical source Falling or injury after contact with electricity

Injuries that can result from Arc Flash are as follows:

Burns from the high temperatures produced by the arc Blindness from the ultra-violet light produced by the arc Hearing loss caused by the pressure wave from the arc blast

Not surprisingly there is legislation in place that aims to regulate these hazards. The three main ones are:

Health and Safety at Work – Primary piece of legislation covering occupational health and safety in Great Britain. It sets out the general duties which:

employers have towards employees and members of the public employees have to themselves and to each other certain self-employed have towards themselves and others

The Electricity at Work Regulations – Expand on the rules regarding electrical safety in teh Health and Safety at Work Act 1974. Employers are given duties and resonsibilites to make sure that all work activity that uses or may be affected by electricity is done safely, and that all foreseeable risks are assessed and minimised as much as possible. Management of Health & Safety at Work Regulations 1999 – Employers are required to undertake an assessment of the risks to the health and safety of their employees and other people who may be affected by their work activity.

We will now try to answer the question: What should you have in place to manage electrical risk? In a nutshell, it is important have an Electrical Safety Management System in place. What does that consist of, you may ask? It depends upon the size of your organisation, but let us assume you are a large company, you should have something like the following in place:

What is the one hand rule in electricity?

How Much Electric Current is Harmful? – The answer to that question also depends on several factors. Individual body chemistry has a significant impact on how electric current affects an individual. Some people are highly sensitive to current, experiencing involuntary muscle contraction with shocks from static electricity.

Others can draw large sparks from discharging static electricity and hardly feel it, much less experience a muscle spasm. Despite these differences, approximate guidelines have been developed through tests that indicate very little current being necessary to manifest harmful effects (again, see the end of the chapter for information on the source of this data).

All current figures given in milliamps (a milliamp is equal to 1/1000 of an amp):

Slight sensation felt at hand(s) Men 1.0 mA 0.4 mA 7mA
Women 0.6 mA 0.3 mA 5 mA
Threshold of Pain Men 5.2 mA 1.1 mA 12 mA
Women 3.5 mA 0.7 mA 8 mA
Painful, but voluntary muscles control maintained Men 62 mA 9 mA 55 mA
Women 41 mA 6 mA 37 mA
Painful, unable to let go of wires Men 76 mA 16 mA 75 mA
Women 60 mA 15 mA 63 mA
Severe pain, difficulty breathing Men 90 mA 23 mA 94 mA
Women 60 mA 15 mA 63 mA
Possible heart fibrillation after 3 seconds Men and Women 500 mA 100 mA

Hz” stands for the unit Hertz, It is the measure of how rapidly alternating current alternates, otherwise known as frequency, So, the column of figures labeled “60 Hz AC” refers to a current that alternates at a frequency of 60 cycles (1 cycle = period of time where current flows in one direction, then the other direction) per second.

The last column, labeled “10 kHz AC,” refers to alternating current that completes ten thousand (10,000) back-and-forth cycles each and every second. Keep in mind that these figures are only approximate, as individuals with different body chemistry may react differently. It has been suggested that an across-the-chest current of only 17 milliamps AC is enough to induce fibrillation in a human subject under certain conditions.

Most of our data regarding induced fibrillation come from animal testing. Obviously, it is not practical to perform tests of induced ventricular fibrillation on human subjects, so the available data is sketchy. Oh, and in case you’re wondering, I have no idea why women tend to be more susceptible to electric currents than men! Suppose I were to place my hands across the terminals of an AC voltage source at 60 Hz (60 cycles per second).

How much voltage would be necessary on this clean, dry-skin condition to produce a current of 20 milliamps (enough to cause me to become unable to let go of the voltage source)? We can use Ohm’s Law to determine this: E = IR E = (20 mA)(1 M \Omega) \textbf Bear in mind that this is a “best case” scenario (clean, dry skin) from the standpoint of electrical safety and that this figure for voltage represents the amount necessary to induce tetanus.

Far less would be required to cause a painful shock! Also, keep in mind that the physiological effects of any particular amount of current can vary significantly from person to person and that these calculations are rough estimates only, With water sprinkled on my fingers to simulate sweat, I was able to measure a hand-to-hand resistance of only 17,000 ohms (17 kΩ).

  1. Bear in mind that this is only with one finger of each hand contacting a thin metal wire.
  2. Recalculating the voltage required to cause a current of 20 milliamps, we obtain this figure: E = IR E = (20 mA)(17 k \Omega) \textbf In this realistic condition, it would only take 340 volts of potential from one of my hands to the other to cause 20 milliamps of current.

However, it is still possible to receive a deadly shock from less voltage than this. Provided a much lower body resistance figure augmented by contact with a ring (a band of gold wrapped around the circumference of one’s finger makes an excellent contact point for electrical shock) or full contact with a large metal object such as a pipe or metal handle of a tool, the body resistance figure could drop as low as 1,000 ohms (1 kΩ), allowing an even lower voltage to present a potential hazard.

E = IR E = (20 mA)(1 k \Omega) \textbf Notice that in this condition, 20 volts is enough to produce a current of 20 milliamps through a person; enough to induce tetanus. Remember, it has been suggested a current of only 17 milliamps may induce ventricular (heart) fibrillation. With a hand-to-hand resistance of 1000 Ω, it would only take 17 volts to create this dangerous condition.

E = IR E = (17 mA)(1 kW) \textbf Seventeen volts is not very much as far as electrical systems are concerned. Granted, this is a “worst-case” scenario with 60 Hz AC voltage and excellent bodily conductivity, but it does stand to show how little voltage may present a serious threat under certain conditions.

  • The conditions necessary to produce 1,000 Ω of body resistance don’t have to be as extreme as what was presented (sweaty skin with contact made on a gold ring).
  • Body resistance may decrease with the application of voltage (especially if tetanus causes the victim to maintain a tighter grip on a conductor) so that with constant voltage a shock may increase in severity after initial contact.

What begins as a mild shock—just enough to “freeze” a victim so they can’t let go—may escalate into something severe enough to kill them as their body resistance decreases and current correspondingly increases. Research has provided an approximate set of figures for electrical resistance of human contact points under different conditions:

Situation Dry Wet
Wire touched by finger 40,000 Ω – 1,000,000 Ω 4,000 Ω – 15,000 Ω
Wire held by hand 15,000 Ω – 50,000 Ω 3,000 Ω – 5,000 Ω
Metal pliers held by hand 5,000 Ω – 10,000 Ω 1,000 Ω – 3,000 Ω
Contact with the palm of hand 3,000 Ω – 8,000 Ω 1,000 Ω – 2,000 Ω
1.5-inch metal pipe grasped by one hand 1,000 Ω – 3,000 Ω 500 Ω – 1,500 Ω
1.5 inch metal pipe grasped by two hands 500 Ω – 1,500 kΩ 250 Ω – 750 Ω
Hand immersed in conductive liquid 200 Ω – 500 Ω
Foot immersed in conductive liquid 100 Ω – 300 Ω

Note the resistance values of the two conditions involving a 1.5-inch metal pipe. The resistance measured with two hands grasping the pipe is exactly one-half the resistance of one hand grasping the pipe. Figure 1.8 With two hands, the bodily contact area is twice as great as with one hand. This is an important lesson to learn: electrical resistance between any contacting objects diminishes with increased contact area, all other factors being equal. With two hands holding the pipe, the current has two, parallel routes through which to flow from the pipe to the body (or vice-versa). Figure 1.9 As we will see in a later chapter, parallel circuit pathways always result in less overall resistance than any single pathway considered alone. In industry, 30 volts is generally considered to be a conservative threshold value for dangerous voltage.

The cautious person should regard any voltage above 30 volts as threatening, not relying on normal body resistance for protection against shock. That being said, it is still an excellent idea to keep one’s hands clean and dry and remove all metal jewelry when working around electricity. Even around lower voltages, metal jewelry can present a hazard by conducting enough current to burn the skin if brought into contact between two points in a circuit.

Metal rings, especially, have been the cause of more than a few burnt fingers by bridging between points in a low-voltage, high-current circuit. Also, voltages lower than 30 can be dangerous if they are enough to induce an unpleasant sensation, which may cause you to jerk and accidentally come into contact across a higher voltage or some other hazard.

I recall once working on an automobile on a hot summer day. I was wearing shorts, my bare leg contacting the chrome bumper of the vehicle as I tighten battery connections. When I touched my metal wrench to the positive (ungrounded) side of the 12-volt battery, I could feel a tingling sensation at the point where my leg was touching the bumper.

The combination of firm contact with metal and my sweaty skin made it possible to feel a shock with only 12 volts of electrical potential. Thankfully, nothing bad happened but had the engine been running and the shock felt at my hand instead of my leg, I might have reflexively jerked my arm into the path of the rotating fan, or dropped the metal wrench across the battery terminals (producing large amounts of current through the wrench with lots of accompanying sparks).

This illustrates another important lesson regarding electrical safety; that electric current itself may be an indirect cause of injury by causing you to jump or spasm parts of your body into harm’s way. The path current takes through the human body makes a difference as to how harmful it is. Current will affect whatever muscles are in its path, and since the heart and lung (diaphragm) muscles are probably the most critical to one’s survival, shock paths traversing the chest are the most dangerous.

This makes the hand-to-hand shock current path a very likely mode of injury and fatality. To guard against such an occurrence, it is advisable to only use one hand to work on live circuits of hazardous voltage, keeping the other hand tucked into a pocket so as to not accidentally touch anything.

Of course, it is always safer to work on a circuit when it is unpowered, but this is not always practical or possible. For one-handed work, the right hand is generally preferred over the left for two reasons: most people are right-handed (thus granting additional coordination when working), and the heart is usually situated to the left of center in the chest cavity.

For those who are left-handed, this advice may not be the best. If such a person is sufficiently uncoordinated with their right hand, they may be placing themselves in greater danger by using the hand they’re least comfortable with, even if shock current through that hand might present more of a hazard to their heart.

  • The relative hazard between shock through one hand or the other is probably less than the hazard of working with less than optimal coordination, so the choice of which hand to work with is best left to the individual.
  • The best protection against shock from a live circuit is resistance, and resistance can be added to the body through the use of insulated tools, gloves, boots, and other gear.

Current in a circuit is a function of available voltage divided by the total resistance in the path of the flow. As we will investigate in greater detail later in this book, resistances have an additive effect when they’re stacked up so that there’s only one path for current to flow: Figure 1.10 Person in direct contact with voltage source: current limited only by body resistance. I = \frac } Now we’ll see an equivalent circuit for a person wearing insulated gloves and boots: Figure 1.11 Person wearing insulating gloves and boots; Current now limited by circuit resistance: I = \frac +R_ +R_ +} Because electric current must pass through the boot and the body and the glove to complete its circuit back to the battery, the combined total ( sum ) of these resistances opposes the flow of current to a greater degree than any of the resistances considered individually.

Safety is one of the reasons electrical wires are usually covered with plastic or rubber insulation: to vastly increase the amount of resistance between the conductor and whoever or whatever might contact it. Unfortunately, it would be prohibitively expensive to enclose power line conductors’ insufficient insulation to provide safety in case of accidental contact.

So safety is maintained by keeping those lines far enough out of reach so that no one can accidentally touch them. If at all possible, shut off the power to a circuit before performing any work on it. You must secure all sources of harmful energy before a system may be considered safe to work on.

Harm to the body is a function of the amount of shock current. Higher voltage allows for the production of higher, more dangerous currents. Resistance opposes current, making high resistance a good protective measure against shock. Any voltage above 30 is generally considered to be capable of delivering dangerous shock currents. Metal jewelry is definitely bad to wear when working around electric circuits. Rings, watchbands, necklaces, bracelets, and other such adornments provide excellent electrical contact with your body and can conduct current themselves enough to produce skin burns, even with low voltages. Low voltages can still be dangerous even if they’re too low to directly cause shock injury. They may be enough to startle the victim, causing them to jerk back and contact something more dangerous in the near vicinity. When necessary to work on a “live” circuit, it is best to perform the work with one hand so as to prevent a deadly hand-to-hand (through the chest) shock current path. If at all possible, shut off the power to a circuit before performing any work on it.

When working on equipment, remove all sources of power before performing any work. In industry, removing these sources of power from a circuit, device, or system is commonly known as placing it in a Zero Energy State, The focus of this lesson is, of course, electrical safety.

Dangerous voltage Spring pressure Hydraulic (liquid) pressure Pneumatic (air) pressure Suspended weight Chemical energy (flammable or otherwise reactive substances) Nuclear energy (radioactive or fissile substances)

Voltage by its very nature is a manifestation of potential energy. In the first chapter, I even used the elevated liquid as an analogy for the potential energy of voltage, having the capacity (potential) to produce a current (flow), but not necessarily realizing that potential until a suitable path for flow has been established and resistance to flow is overcome.

  1. A pair of wires with a high voltage between them do not look or sound dangerous even though they harbor enough potential energy between them to push deadly amounts of current through your body.
  2. Even though that voltage isn’t presently doing anything, it has the potential to, and that potential must be neutralized before it is safe to physically contact those wires.

All properly designed circuits have “disconnect” switch mechanisms for securing voltage from a circuit. Sometimes these “disconnects” serve a dual purpose of automatically opening under excessive current conditions, in which case we call them “circuit breakers”.

  • Other times, the disconnecting switches are strictly manually-operated devices with no automatic function.
  • In either case, they are there for your protection and must be used properly.
  • Please note that the disconnect device should be separate from the regular switch used to turn the device on and off.

It is a safety switch, to be used only for securing the system in a Zero Energy State: Figure 1.12 With the disconnect switch in the “open” position as shown (no continuity), the circuit is broken and no current will exist. There will be zero voltage across the load, and the full voltage of the source will be dropped across the open contacts of the disconnect switch. Figure 1.13 With the temporary ground connection in place, both sides of the load wiring are connected to ground, securing a Zero Energy State at the load. Since a ground connection made on both sides of the load is electrically equivalent to short-circuiting across the load with a wire, that is another way of accomplishing the same goal of maximum safety: Figure 1.14 Either way, both sides of the load will be electrically common to the earth, allowing for no voltage (potential energy) between either side of the load and the ground people stand on. This technique of temporarily grounding conductors in a de-energized power system is very common in maintenance work performed on high voltage power distribution systems.

A further benefit of this precaution is protection against the possibility of the disconnect switch being closed (turned “on” so that circuit continuity is established) while people are still contacting the load. The temporary wire connected across the load would create a short-circuit when the disconnect switch was closed, immediately tripping any overcurrent protection devices (circuit breakers or fuses) in the circuit, which would shut the power off again.

Damage may very well be sustained by the disconnect switch if this were to happen, but the workers at the load are kept safe. It would be good to mention at this point that overcurrent devices are not intended to provide protection against electric shock.

  1. Rather, they exist solely to protect conductors from overheating due to excessive currents.
  2. The temporary shorting wires just described would indeed cause any overcurrent devices in the circuit to “trip” if the disconnect switch were to be closed, but realize that electric shock protection is not the intended function of those devices.

Their primary function would merely be leveraged for the purpose of worker protection with the shorting wire in place.