WHAT IS HIERARCHY OF CONTROL

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hierarchy of control in safety
The following is the general hierarchy of control: Elimination Substation Engineering controls Administrative controls with warnings and signage Personal protective equipment.

HIERARCHY OF CONTROL

While doing the risk assessment, if risks are high then we need to introduce control measures to bring down the risk. In order to ensure that the risk assessor selected the best available option, the hierarchy of risk is created, wherein the topmost control measure in the list is the most preferred while the bottom-most is the least preferred. These control measures are based on the principle of a safe place and a safe person. The top three in the list create a safe place, while the bottom two create a safe person and hence are less preferred.    

The following is the general hierarchy of control:

  1. Elimination
  2. Substitution
  3. Engineering controls
  4. Administrative controls with warnings and signage
  5. Personal protective equipment.

1. Elimination: HIERARCHY OF CONTROL

The best and most preferred option is to eliminate the hazard. If a group of managers needs to travel from one city to the other to attend a meeting, the same can be done by using video conferencing, thus eliminating the hazard of traveling .robots can be deployed where are risks of manual handling and repeated movements of the limbs.

2. Substitution: HIERARCHY OF CONTROL

When hazards can’t be fully eliminated then the option of substitution needs to be tried. Substitution can be done in many ways. Following are some of the examples:

  • Using a less flammable liquid instead of a highly flammable one
  • Using railways instead of road travel.
  • Handling material using handling aids like trolleys instead of manual handling.
  • Use of compressed air as a source of power instead of electricity

3. Engineering controls: HIERARCHY OF CONTROL

 

This creates engineered solutions to prevent exposure to the hazards. The principle used here is to create a barrier between the worker and the hazards. There is the various way to doing it.

  • Isolation or total enclosure: in this, the hazard is isolation so that it cannot cause harm, like for example and the toxic chemical is handle in fume cupboard thereby preventing its release into the atmosphere and hence the working on it or nearby need not wear breathing apparatus.
  • Separation or segregation: it is placing the hazard in an inaccessible location. For example, the high voltage wires are placed overhead high enough to prevent anybody from reaching it. Separation or segregation could also mean having separate walkways for pedestrians and vehicles separated by hard barrication.
  • Partial enclosure: in this, the hazard is partially enclosed for ease of operation. A wooden saw cutter would have a partial guard on it allowing the wood to be passed through for the cutting operation to be accomplished.
  • Safety devices: this would include devices which are activated in the presence of certain hazards. For example, a fuse would break off the electrical supply in case of an overload current protecting the equipment and a subsequent fire hazard. Similarly, an RDC would trip off the supply if fault current is detected.

4. Administrative controls with warnings and signage:

Zazardous area classification

These rely on procedures and behavior.

  • Written procedures/ safe system of work: operating procedures or safe system of work is probably the most common form of control measure used in industry today and may be the most economical and, in some cases, the only practical way of managing a particular risk. They should allow for methodical execution of tasks. The development of safe operating procedures should address the hazards that have been identified in the risk assessment process. If the risks involved in the task are high or medium, the detail of the system should be in writing and should be communicated to the employee formally in a training session. Details of the system for low-risk activities may be conveyed verbally. There must be records that the employee (or contractor) had training provided in the safe system of work and that they understand it and will abide by it.
  • Reduce time of exposure: this involves reducing the time during the working day that the employee is exposed to the hazard, by the giving the employee either other work or rest periods. It is normally only suitable for the control of health hazards associated with, for example, noise, vibration, excessive heat or cold, display screens, and hazardous substances.
  • Information, instruction, and training: any operation of equipment or process needs to be done only by competent people. Competence can be achieved by adequate training and awareness created by providing them with information and instruction so that they are fully aware of the hazards in their workplace.
  • Supervision: this is how management routinely keeps a check on the behavior of the workers. Supervision ensures that the workers are following the safe system of work and the controls are in place and been used appropriately. The level of supervision will depend upon the risk levels present.

Safety signs

Safety and/or health sign: it is a type of sign which provides information about potential hazards, emergency exits, and fire protection equipment in the work environment. The information can be conveyed by means of

  1. Signboard
  2. Colour
  3. Illuminated sign
  4. Acoustic signal
  5. Verbal communication
  6. Hand signage

 Signboard:

it is a type of board that provides information of instruction by the combination of shape, color, and a symbol. These boards not only consist of written text but also consist of pictograms to overcome the language barrier.

Following are the type of signboards:

Prohibition:  round in shape, red edging with the diagonal crossbar on a white background, the symbol within the circle to be black denoting a safety sign that indicates that certain behavior is prohibited. The red part shall be 35%.

Warning: the triangle shapes with black border and symbol within the yellow area denoting a safety sign that gives warning of a hazard. The yellow part shall be 50%.

Mandatory: round in shape, the white pictogram on blue background and blue shall be 50%.

Safe condition: oblong or square in shape with white pictogram on green background and green shall be 50%.

Fire equipment: a red oblong or square in with pictogram on a red background denoting a safety sign that indicated the location of fire-fighting equipment. The red portion shall be 50% here as during the emergency, the power failure will be there and hence this shall be visible in emergency lighting.

Safety color:  a color is defined with a specific meaning with respect to safety (e.g. yellow means ‘be careful’ or ‘take precaution’).

Symbol or pictogram: it is used on a signboard or illuminated sign to overcome the language barrier (e.g. the trefoil ionizing radiation warning sign).

Illuminated sign:  a sign made of the transparent or translucent material which is illuminated from the inside or the rear to give the appearance of a luminous surface (e.g. emergency exits sign).

Acoustic signal: a sound signal which is transmitted without any manual interventions (e.g. a fire alarm).

Verbal communication: communication of a predetermined spoken message by a human or artificial voice.

Hand signal:  it provided an easy means of communication with movement or position of the arm or hands and helps to execute maneuvers operation with ease.

Sign for marking obstacles and dangerous locations

Red and white stripes indicate entry with permission only. Black and yellow strips indicate entry can be without permission, but with precautions taken.

5. Personal protective equipment (PPE):

Safety manager requirement 

These should be considered as a last resort only when the other controls measures are not practically feasible or they are not fully controlling the risks. The generally create a second life of defense. There is various type of PPE.

  • Helmet for protecting the head against falling objects.
  • Goggles and visors for protecting the eyes against flying objects of fume.
  • Hand gloves to protect the skin against absorbing dangerous chemicals.
  • Ear defenders to protect against loud noise.
  • Respiratory protection devices to protect against dust, vapor, and fumes which could be inhaled.

Following are the benefits of PPE:

  • It gives immediate protection to allow a job to continue while engineering controls are put in place;
  • In an emergency it can be the only practicable way of effect the ing rescue or shutting the own plant in the hazardous atmosphere;
  • It can be used to carry out work in confined spaces where alternatives are impracticable. But it should never be used to allow people to work in dangerous atmospheres, which are, for example, enriched with oxygen or potentially explosive.

Following are the limitations of PPE:

  • Only protects the person wearing the equipment, not others nearby.
  • Relies on people wearing the equipment at all times.
  • Must be used properly.
  • Must be replaced when it no longer offers the correct level of protection. This last point is particularly relevant when respiratory protection is used.
  • It may increase the overall risk by impairing the senses, for example, goggles may mist thereby causing impaired vision.
  • They may be incompatible thereby reducing its protection. For example, eye protection may interfere with the ear muffs.
  • If it fails, it fails to danger and mat often gets contaminated if not stored correctly.
  • It is expensive in the long run.

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