Indoor air quality testing may be necessary to ensure employee safety. Testing and monitoring may be applied to those conditions where employees may be exposed to:
nitrogen dioxide and sulfur dioxide
landfill gases
noxious odors
radon gas
factory emissions
odor complaints
rainwater
metals
smoke levels
dust
volatile organic compounds
indoor air quality (including Carbon Monoxide)
The results of air quality testing may be used to:
• Assign levels of worker respiratory protection
• For emergency planning
Methods of Sampling and Testing
Electric Power producers shall provide adequate means of carrying air monitoring in generator houses, transmitting stations, injection and switching substations, etc.
Three main methods are available to measure air pollution:
Passive Sampling: This refers to absorption or diffusion tubes or badges that provide a simple and inexpensive indication of average pollution levels over a period of weeks or months. Plastic tubes or discs open at one end to the atmosphere and with a chemical absorbent at the other, collect a sample for subsequent analysis in the laboratory.
The low cost per tube allows sampling at a number of points and is useful in highlighting "hotspots" where more detailed study may be needed. The quality and accuracy of the data from passive sampling tubes does not make them suitable for precise measurements but they can give useful long term trend data.
Active Sampling: This involves the collection of samples, by physical or chemical means, for subsequent laboratory analysis. Typically, a known volume of air is pumped through a filter or chemical collector for a known period of time - the collection medium is then subjected to laboratory analysis. This method is not suitable for continuous or near-real time air quality monitoring.
Automatic Sampling: This is the most sophisticated method of air quality analysis, producing high-resolution measurement data of a range of pollutants. The pollutants that can be measured include, but are not limited to, NOx, S02 CO, 03, VOCs, PM10, PM2.5, Carbon Black, Hg, Benzene etc. The air quality is continuously sampled and measured on-line and in real-time.
The real time data is stored, typically as one hourly averages, with data being collected remotely from individual monitoring stations by telemetry. Remote control of the monitoring and data system is also possible as is remote diagnostics for most of the analyzers.
DANGER OF POWER TOOLS - WHAT ARE THE DANGER OF POWER TOOLS BASICS
Be extra careful in handling power tools.
Power tools are determined by their power source: electric, pneumatic, liquid fuel, hydraulic, and powder-actuated. Power tools should be equipped with guards and safety switches.
Personal protective equipment such as safety goggles and gloves should be worn to protect against hazards that may be encountered while using power tools.
To prevent hazards associated with the use of power tools, workers should observe the following general precautions:
1 Never carry a tool by the cord or hose.
2 Never yank the cord or the hose to disconnect it from the receptacle.
3 Keep cords and hoses away from heat, oil, and sharp edges.
4 Disconnect tools when not using them, before servicing and cleaning them, and when changing accessories
such as blades, bits, and cutters.
5 Keep all people not involved with the work at a safe distance from the work area.
6 Secure work with clamps or a vise, freeing both hands to operate the tool.
7 Avoid accidental starting. Do not hold fingers on the switch button while carrying a plugged-in tool.
8 Maintain tools with care; keep them sharp and clean for best performance.
9 Follow instructions in the user's manual for lubricating and changing accessories.
10 Be sure to keep good footing and maintain good balance when operating power tools.
11 Wear proper apparel for the task. Loose clothing, ties, or jewelry can become caught in moving parts.
Remove all damaged portable electric tools from use and tag them:
"Do Not Use.
Power tools are determined by their power source: electric, pneumatic, liquid fuel, hydraulic, and powder-actuated. Power tools should be equipped with guards and safety switches.
Personal protective equipment such as safety goggles and gloves should be worn to protect against hazards that may be encountered while using power tools.
To prevent hazards associated with the use of power tools, workers should observe the following general precautions:
1 Never carry a tool by the cord or hose.
2 Never yank the cord or the hose to disconnect it from the receptacle.
3 Keep cords and hoses away from heat, oil, and sharp edges.
4 Disconnect tools when not using them, before servicing and cleaning them, and when changing accessories
such as blades, bits, and cutters.
5 Keep all people not involved with the work at a safe distance from the work area.
6 Secure work with clamps or a vise, freeing both hands to operate the tool.
7 Avoid accidental starting. Do not hold fingers on the switch button while carrying a plugged-in tool.
8 Maintain tools with care; keep them sharp and clean for best performance.
9 Follow instructions in the user's manual for lubricating and changing accessories.
10 Be sure to keep good footing and maintain good balance when operating power tools.
11 Wear proper apparel for the task. Loose clothing, ties, or jewelry can become caught in moving parts.
Remove all damaged portable electric tools from use and tag them:
"Do Not Use.
LEGAL ASPECTS OF RISK ASSESSMENT ON ELECTRICAL WORKS BASIC INFORMATION
The general duties of employers to their employees in section 2 of the Health and Safety at Work Act 1974 imply the need for risk assessment. This duty was also extended by section 3 of the Act to anybody else
affected by activities of the employer – contractors, visitors, customers or members of the public.
However, the Management of Health and Safety at Work Regulations are much more specific concerning the need for risk assessment. The following requirements are laid down in those regulations: the risk assessment shall be ‘suitable and sufficient’ and cover both employees and non-employees affected by the employer’s undertaking (e.g. contractors, members of the public, students, patients, customers, etc.); every self-employed person shall make a ‘suitable and sufficient’ assessment of the risks to which they or those affected by the undertaking may be exposed; any risk assessment shall be reviewed if there is reason to suspect that it is no longer valid or if a significant change has taken place; where there are more than four employees,
the significant findings of the assessment shall be recorded and any specially at risk group of employees identified. (This does not mean that employers with four or less employees need not undertake risk assessments.)
The term ‘suitable and sufficient’ is important since it defines the limits to the risk assessment process. A suitable and sufficient risk assessment should:
➤ identify the significant risks and ignore the trivial ones;
➤ identify and prioritize the measures required to comply with any relevant statutory provisions;
➤ remain appropriate to the nature of the work and valid over a reasonable period of time.
When assessing risks under the Management of Health and Safety at Work Regulations, reference to other regulations may be necessary even if there is no specific requirement for a risk assessment in those regulations.
For example, reference to the legal requirements of the Provision and Use of Work Equipment Regulations will be necessary when risks from the operation of machinery are being considered. However, there is no need to repeat a risk assessment if it is already covered by other regulations (e.g. a risk assessment involving
personal protective equipment is required under the COSHH Regulations so there is no need to undertake a
separate risk assessment under the Personal Protective Equipment Regulations).
Apart from the duty under the Management of Health and Safety at Work Regulations to undertake a health
and safety risk assessment of any person (employees, contractors or members of the public), who may be affected by the activities of the organization, the following regulations require a specific risk assessment to be made:
➤ Ionising Radiation Regulations
➤ Control of Asbestos Regulations
➤ The Control of Noise at Work Regulations
➤ Manual Handling Operations Regulations
➤ Health and Safety (Display Screen Equipment)
➤ The Personal Protective Equipment at Work Regulations
➤ The Confined Spaces Regulations
➤ Work at Height Regulations
➤ The Regulatory Reform (Fire Safety) Order
➤ The Control of Vibration at Work Regulations
➤ Control of Lead at Work Regulations
➤ Control of Substances Hazardous to Health Regulations.
A detailed comparison of the risk assessments required for most of these and more specialist regulations is given in the HSE Guide to Risk Assessment Requirements, INDG218.
affected by activities of the employer – contractors, visitors, customers or members of the public.
However, the Management of Health and Safety at Work Regulations are much more specific concerning the need for risk assessment. The following requirements are laid down in those regulations: the risk assessment shall be ‘suitable and sufficient’ and cover both employees and non-employees affected by the employer’s undertaking (e.g. contractors, members of the public, students, patients, customers, etc.); every self-employed person shall make a ‘suitable and sufficient’ assessment of the risks to which they or those affected by the undertaking may be exposed; any risk assessment shall be reviewed if there is reason to suspect that it is no longer valid or if a significant change has taken place; where there are more than four employees,
the significant findings of the assessment shall be recorded and any specially at risk group of employees identified. (This does not mean that employers with four or less employees need not undertake risk assessments.)
The term ‘suitable and sufficient’ is important since it defines the limits to the risk assessment process. A suitable and sufficient risk assessment should:
➤ identify the significant risks and ignore the trivial ones;
➤ identify and prioritize the measures required to comply with any relevant statutory provisions;
➤ remain appropriate to the nature of the work and valid over a reasonable period of time.
When assessing risks under the Management of Health and Safety at Work Regulations, reference to other regulations may be necessary even if there is no specific requirement for a risk assessment in those regulations.
For example, reference to the legal requirements of the Provision and Use of Work Equipment Regulations will be necessary when risks from the operation of machinery are being considered. However, there is no need to repeat a risk assessment if it is already covered by other regulations (e.g. a risk assessment involving
personal protective equipment is required under the COSHH Regulations so there is no need to undertake a
separate risk assessment under the Personal Protective Equipment Regulations).
Apart from the duty under the Management of Health and Safety at Work Regulations to undertake a health
and safety risk assessment of any person (employees, contractors or members of the public), who may be affected by the activities of the organization, the following regulations require a specific risk assessment to be made:
➤ Ionising Radiation Regulations
➤ Control of Asbestos Regulations
➤ The Control of Noise at Work Regulations
➤ Manual Handling Operations Regulations
➤ Health and Safety (Display Screen Equipment)
➤ The Personal Protective Equipment at Work Regulations
➤ The Confined Spaces Regulations
➤ Work at Height Regulations
➤ The Regulatory Reform (Fire Safety) Order
➤ The Control of Vibration at Work Regulations
➤ Control of Lead at Work Regulations
➤ Control of Substances Hazardous to Health Regulations.
A detailed comparison of the risk assessments required for most of these and more specialist regulations is given in the HSE Guide to Risk Assessment Requirements, INDG218.
LOW VOLTAGE SYSTEM EARTHING BASIC INFORMATION AND TUTORIALS
For many years the Regulations required
that each l.v. system should be solidly connected to earth at only
one point, that being the neutral of the source transformer. Special
permission was necessary to earth at more than one point.
The Regulations also required that
cables buried in the highway must have a metallic sheath. Systems
earthed at only one point require the neutral conductor to be
electrically separate and are now known as SNE (separate neutral and
earth).
It was, and still is, the
responsibility of each consumer to provide the earth connection for
his own installation. This was commonly achieved by connection to a
metallic pipe water main.
The growing use of PVC water mains
makes this impossible for new installations and causes problems with
existing ones when water mains are replaced. Gradually, supply
companies developed a practice of providing consumers with an earth
terminal connected to the sheath of their service cable.
This is, of course, a very satisfactory
arrangement but it is not universally practical as many cables laid
in the 1920s or earlier are still in use and many of these are not
bonded across at joints. The arrangement is not practical on most
overhead systems.
In Germany and elsewhere in Europe an
earthing system known as ‘nulling’ grew up. This employed the
principle of earthing the neutral at as many points as possible.
It simplified the problem of earthing
in high resistance areas and by combining the sheath with the neutral
conductor permitted a cheaper cable construction. These benefits were
attractive and during the 1960s the official attitude in the UK
gradually changed to permit and then encourage a similar system known
as PME (protective multiple earthing).
Blanket approvals for the use of this
system, and the required conditions to be met, were finally given to
all area boards in 1974. In BS 7671 – the 16th edition of the IEE
Wiring Regulations this system is classified as TN-C-S.
Providing the consumer with an earth
terminal which is connected to the neutral conductor ensures that
there is a low impedance path for the return of fault currents, but
without additional safeguards there are possibilities of dangerous
situations arising under certain circumstances.
If the neutral conductor becomes
disconnected from the source of supply then the earthed metalwork in
the consumer’s premises would be connected via any load to the live
conductor and thus present an electric shock hazard from any
metalwork not bonded to it, but which has some connection with earth.
In order to eliminate this rare potential hazard the Secretary of
State, in his official Regulations, requires that all accessible
metalwork should be bonded together as specified in the IEEE Wiring Regulations and so render the
consumer’s premises a ‘Faraday cage’. This is the reason for
the more stringent bonding regulations associated with PME.
Under the extremely rare circumstances
of a broken service neutral and intact phase conductor, there may be
a danger of electric shock on the perimeter of the ‘cage’ to
someone using an earthed metal appliance in a garden, even though the
appliance may be protected by an RCD (residual current device) in
accordance with the IEE Wiring Regulations. For the same reason metal
external meter cabinets are undesirable.
In order to eliminate as far as
possible the chance of a completely separated neutral, a number of
precautions are taken. First, all cables must be of an approved type
with a concentric neutral, either solid or stranded, of sufficient
current carrying capacity.
Secondly the neutral conductor of a
spur end on the system is connected to an earth electrode if more
than four consumers’ installations are connected to the spur, or if
the length of the spur connection from the furthest connected
consumer to the distributing main exceeds 40 metres.
Where reasonably practicable, cable
neutrals are joined together to form duplicate earth connections. A
faulty or broken neutral will give an indication of its presence by
causing supply voltages to fluctuate, which, of course, should be
reported to the local DNO as soon as possible. All these measures
contribute to a system which is as safe as practicable and
self-monitoring.
It is the declared intention of the EI
in the UK to provide earth terminals wherever required and
practicable within the foreseeable future. The local DNO should be
contacted regarding their requirements for the use of PME earth
terminals for TN-C-S systems.
SWITCHING TRANSIENT LOADING EFFECTS ON THE SYSTEM BASIC INFORMATION AND TUTORIALS
One of the primary uses of electricity
is for general lighting and the local DNO must ensure that its supply
is suitable for this purpose. Repeated sudden changes in voltage of a
few per cent are noticeable and are likely to cause annoyance.
The local DNO must ensure that these
sudden variations are kept within acceptable levels and this means
placing limits on consumers’ apparatus which demands surges of
current large enough to cause lighting to flicker.
In order to evaluate flicker in
measurable terms, two levels have been selected: the threshold of
visibility and the threshold of annoyance.
Both are functions of
frequency of occurrence as well as voltage change.
Since both these thresholds are
subjective it has been necessary to carry out experiments with
various forms of lighting and panels of observers to ascertain
consensus relationships between frequency of occurrence and
percentage voltage change for the two thresholds.
The DNOs have used this information in
setting the planning levels for flicker contained in Engineering
Recommendation P28, which govern motor starting currents, etc.
The network impedance from the source
to the point of common coupling between the lighting and the
offending load is of paramount importance and thus the local office
of the DNO should be consulted in cases where the possibility of
creating an annoyance arises.
Intermittently loaded or frequently
started motors, such as those on lifts, car crushers, etc., together
with instantaneous water heaters, arc welders and furnaces, are all
potential sources of disturbance.
Large electric furnaces present a
particular problem and it is frequently necessary to connect them to
a higher voltage system than is necessary to meet their load in order
to achieve a lower source impedance.
Fluctuations occurring about ten times
a second exhibit the maximum annoyance to most people, but even those
as intermittent as one or two an hour will annoy if the step change
is of sufficient magnitude.
CENELEC Standard EN61000-3-3, limits
voltage fluctuation emissions from equipment rated less than or equal
to 16 A and EN61000-3-11 limits emissions from equipment rated from
16 A to 75A.
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