Physical hazards consists of occupational noise, vibration, inappropriate illumination, ventilation, ionizing and non ionizing radiation etc. Our hearing sensory will cause serious defects by noise and vibration

1. OHH Unit-1
NOISE, VIBRATION, VENTILATION, LIGHTING AND HEAT STRESS

2. Working Environment
Lighting Thermal
Vibration
Noise
Space
Ventilation
BIT

3. Noise
• Noise is unwanted sound judged to be unpleasant, loud or disruptive to
hearing.
• From a physics standpoint, noise is indistinguishable from sound, as
both are vibrations through a medium, such as air or water.
• The difference arises when the brain receives and perceives a sound.
• Noise can be annoying and it can interfere with your ability to work by
causing stress and disturbing your concentration.
• Noise can cause accidents by interfering with communication and
warning signals.
• Noise can cause chronic health problems. Noise can also cause you to
lose your hearing.

4. • Hearing loss from exposure to noise in the workplace is one of the most
common of all industrial diseases.
• Workers can be exposed to high noise levels in workplaces as varied as
construction industries, foundries and textile industries.
• Short-term exposure to excessive (too much) noise can cause temporary
hearing loss, lasting from a few seconds to a few days.
• Exposure to noise over a long period of time can cause permanent hearing
loss.
• Hearing loss that occurs over time is not always easy to recognize and
unfortunately, most workers do not realize they are going deaf until their
hearing is permanently damaged.
• Industrial noise exposure can be controlled — often for minimal costs and
without technical difficulty.
• The goal in controlling industrial noise is to eliminate or reduce the noise at
the source producing it.

5. Noise level in industries
Sl.No: Industry dB(A)
1 Pharma 94-120
2 Foundry 104-120
3 Heavy Engineering 94-124
4 Textile 90-117
5 Fertilisers 104-180

6. Health Effects of Noise Exposure
NIHL – Noise Induced Hearing Loss
• The health effects of noise exposure depend on the level of the noise and
the length of the exposure. They are,
1. Temporary hearing loss:
• After spending a short time in a noisy workplace, you may have noticed that you
cannot hear very well, and you have a ringing in your ears.
• This condition is called temporary threshold shift.
• The ringing and the feeling of deafness normally wear off after you have been
away from the noise for a short time.
• However, the longer you are exposed to the noise, the longer it takes for your
hearing to return to “normal”.
• After leaving work, it may take several hours for a worker's ears to recover.
• This may cause social problems because the worker may find it difficult to hear
what other people are saying or may want the radio or television on louder than
the rest of the family.

7. 2. Permanent hearing loss:
• Exposure to excessive noise for too long, your ears do not recover, and the
hearing loss becomes permanent.
• Permanent hearing loss can never be repaired.
• This type of damage to the ear can be caused by long-term exposure to
loud noise or, in some cases, by short exposures to very loud noises.
• When a worker begins to lose his or her hearing, he or she may first notice
that normal talking or other sounds, such as warning signals, are becoming
unclear.
• Workers often adapt themselves (“get used to”) to hearing loss produced
by harmful noises at work.
• For example, they may begin to read lips as people talk, but have difficulty
listening to someone in a crowd or on the telephone.

8. • In order to hear the radio or television they may need to turn up the volume so
much that it deafens the rest of the family. “Getting used to” noise means you
are slowly losing your hearing.
• Hearing tests are the only reliable way to find out whether a worker is suffering
from hearing loss.
• Unfortunately, hearing tests can be difficult to obtain and need to be performed
by a trained health-care professional.
• The reactions of new workers or visitors to a noisy workplace can be indicators
of a noise problem, for example if they have to shout, cover their ears, or leave
“in a hurry”.

9. 3. Other effects:
• In addition to hearing loss, exposure to noise in the workplace can cause a
variety of other problems, including chronic health problems:
• Exposure to noise over a long period of time decreases coordination and
concentration. This increases the chance of accidents happening.
• Noise increases stress, which can lead to a number of health problems,
including heart, stomach and nervous disorders.
• Noise is suspected of being one of the causes of heart disease and stomach
ulcers.
• Workers exposed to noise may complain of nervousness, sleeping problems
and fatigue (feeling tired all the time).
• Excessive exposure to noise can also reduce job performance and may
cause high rates of absenteeism.

10. Measuring Noise
• Noise in the workplace may be disturbing because of its frequency as well
as its volume.
• For example, a high-pitched noise, such as a whistle, irritates the ears much
more than a noise with a low pitch, even if the volume is the same in both
cases.
• Decibels: Sounds have different intensities (loudness). For example, if you
shout at someone instead of whispering, your voice has more energy and
can travel a great distance, therefore it has more intensity (loudness).
• Intensity is measured in units which are calls decibels (dB) or dB(A).
• The decibel scale is not a typical scale — it is a logarithmic scale.
• Basically this means that a small increase in the decibel level is, in reality, a
big increase in the noise level.

11. • For example, if sound is increased by 3 dB at any level, your ears will tell
you that the sound has approximately doubled in volume.
• Similarly, if sound is reduced by 3 dB, your ears will feel that the volume has
been cut in half.
• Therefore, an increase of 3 dB from 90 dB to 93 dB means the volume of
the noise has doubled.
• However, a 10 dB increase at any level (for example, from 80 dB to 90 dB)
means the noise intensity has increased ten times.
• Inside a typical workplace, noise comes from different sources, such as
tools (machinery and materials handling), compressors, background noise,
etc.
• If you want to identify all of the noise problems in the workplace, then you
must measure the noise from each source separately.
• An effective way to measure the noise in your workplace is with a sound
meter.

12. Sound levels and effects on humans

13. Safe Noise Levels:
• A safe level of noise basically depends on two things:
(1) Level (volume) of the noise
(2) How long you are exposed to the noise.
• The level of noise allowed by most countries' noise standards is generally
85-90 dB over an eight-hour workday
• Exposure to higher noise levels may be allowed for periods of less than
eight hours of exposure time.
• For example, workers should not be exposed to noise levels above 95 dB
for more than four hours per day

14. • Exposed workers should be provided with ear protection while exposed at
this level and rotated out of the noise areas after four hours of continuous
work.
• The eight-hour per day exposure limit found in a noise standard is the total
amount of noise that a worker may be exposed to over an eight-hour
period.
• The exposure may be from continuous (constant) noise, or from
intermittent noise (noise that is periodic at regular intervals but not
continuous).
• Therefore, you must add up the levels of noise you are exposed to
throughout the day and see if they exceed 85-90 dB.
• Note: workers should never be exposed to more than 140 dB of impulse
noise (usually a very loud noise that occurs only once) at any time.

15. Recommended limits of noise exposure for the number of hours
No. of hours exposed Sound level dB
8 90
6 92
4 95
3 97
2 100
1.5 102
1 105
0.5 110
0.25 or less 115

16. Methods of noise control
• Workplace noise can be controlled:
(1) at the source
(2) through the use of barriers
(3) at the worker.
1. At the source
• Controlling noise at its source is the best method of noise control.
• It can also often be cheaper than other methods of noise control.
• This method of control may require that some noisy machinery be replaced.
• Noise can be controlled at the source by the manufacturer, so that noisy
devices never reach your workplace.
• Many machines are now required to conform to noise standards

17. • Therefore, before new machines are purchased, checks should be made to see
that they conform to noise standards.
• Noise control at the source can also be engineered into an existing device by
making adjustments to parts or a whole machine that reduce noise.
Methods to reduce noise include:
• preventing or reducing impact between machine parts;
• reducing speeds gently between forward and reverse movements;
• replacing metal parts with quieter plastic parts;
• enclosing particularly noisy machine parts;
• providing mufflers for the air outlets of pneumatic valves;
• changing the type of pump in hydraulic systems;
• changing to quieter types of fans or placing mufflers in the ducts of ventilation
systems;
• providing mufflers for electric motors;
• providing mufflers for intakes of air compressors.

18. • Noise from the way materials are handled can be reduced by measures
such as:
• reducing the dropping height of goods being collected in bins and boxes;
• increasing the rigidity of containers receiving impact from goods, or damping them
with damping materials;
• using soft rubber or plastic to receive hard impacts;
• reducing the speed of conveyor systems;
• using belt conveyors rather than the roller type.

19. 2. Barriers
• If it is not possible to control the noise at the source, then it may be
necessary to enclose the machine, place sound-reducing barriers between
the source and the worker or increase the distance between the worker
and the source.
• The following chart is a simple method of knowing how much sound is
reduced by distance.
• Small sound source produces a sound level of 90 dB at a distance of 1
meter, the sound level at a 2-meter distance is 84 dB, at 4 meters 78 dB,
etc.

20. Here are a few points to remember when controlling noise with barriers:
• An enclosure should not be in contact with any part of the machine;
• Holes in the enclosure should be minimized;
• Access doors and holes for wiring and piping should be fitted with rubber
gaskets;
• Panels of insulating enclosures must be covered inside with sound-
absorbent material;
• Exhausts and air vents must be silenced and directed away from operators;
• The noise source should be separated from other work areas;
• The noise should be deflected away from work areas with a sound-
insulating or reflecting barrier;
• Sound-absorbent materials should be used, if possible, on walls, floors and
ceilings.

21. 3. At the worker
• Controlling noise at the worker, by using ear protection is, unfortunately,
the most common yet least effective form of noise control
• Forcing the worker to adapt to the workplace is always the least desirable
form of protection from any hazard.
• Generally, there are two types of ear protection: earplugs and earmuffs.
Both are designed to prevent excessive noise from reaching the inner ear.
• Earplugs are worn inside the ear and come in a variety of materials,
including rubber, plastic, or any material that will fit tightly in the ear.
• Earplugs are the least desirable type of hearing protection because they
do not provide very effective protection against noise and they can cause
ear infection if pieces of the plug are left in the ear or if a dirty plug is
used.

22. • Cotton wool should not be used as ear protection.
• Earmuffs are more protective than earplugs if they are used correctly.
• They are worn over the whole ear and protect the ear from noise.
• Earmuffs are less efficient if they do not fit tightly or if glasses are worn with
them.
• Ear protection is the least acceptable method of controlling an occupational
noise problem because:
• the noise is still present: it has not been reduced;
• in hot, humid conditions workers often prefer earplugs (which are less effective)
because earmuffs make the ears sweaty and uncomfortable;
• management does not always provide the correct type of ear protection: often it is a
case of “the cheaper the better”;
• workers cannot communicate with each other and cannot hear warning signals;
• if ear protection is provided instead of controlling the noise at source, then
management is putting the responsibility on the worker — it becomes the worker's
fault if he or she becomes deaf.

24. VIBRATION-INTRODUCTION
• Vibrations are mechanical oscillations transmitted to the human body via
direct contact.
• Vibration is caused by work equipment performing continuous or
repetitive movements, such as power-driven tools, or rotating machines.
• The strain caused by vibration results from vibration intensity and the
duration of exposure.
• Engineers, technicians, consultants, and machine designers are focused
on ,
• how physical objects are affected by vibration
• how vibration in the workplace causes serious injury in humans
• How these injuries that could have been prevented with the right amount of
knowledge and the application of a few simple guidelines.

25. • Repeated exposure to high levels of vibration is known to cause injury to
workers over time.
• Based on exactly how these exposures intersect an individual's work
environment, they are classified into two general types
1. Hand-arm vibration (HAV)- direct injury to the fingers and hand,
affecting feeling, dexterity, and grip.
2. Whole-body vibration (WBV)- higher than expected levels of low back
pain and injury in the workforce and is one of the most pervasive
causes of lost time and production output

26. Vibration Measurement
• A complete assessment of exposure to vibration requires the measurement of
1. vibration acceleration in meters per second squared (m/s2)
2. Vibration exposure direction is also important and is measured in defined directions
3. Vibration frequencies and duration of exposure are also determined
4. Hand-grip force- How hard a person grips a tool affects the amount of vibrational
energy entering the hands;
• The amount of exposure is determined by measuring acceleration in the units of m/s2
• Acceleration is often used as a measure of vibration exposure for the following
reasons:
• Several types of instruments are available for measuring acceleration, the rate of change of velocity
in speed or direction per unit time (e.g., per second).
• Measuring acceleration can also give information about velocity and amplitude of vibration.
• The degree of harm is related to the magnitude of acceleration.

27. Instrumentation:
• A typical vibration measurement system includes
1. A device to sense the vibration (accelerometer)
2. An instrument to measure the level of vibration. This equipment also has settings for
measuring frequency, a frequency-weighting network,
3. A display such as a meter, printer or recorder.
• The accelerometer produces an electrical signal.
• The size of this signal is proportional to the acceleration applied to it.
• The frequency-weighting network mimics the human sensitivity to vibration of
different frequencies.

28. • The use of weighting networks gives a single number as a measure of
vibration exposure and is expressed as the frequency-weighted
vibration exposure in meters per second squared (m/s2) units of
acceleration.
• Human hand is not equally sensitive to vibration energy at all
frequencies.
• The sensitivity is the highest around 8-16 Hz (Hertz or cycles per
second).
• Measuring equipment takes this fact into account by using a weighting
network.

29. 1. Hand-arm vibration (HAV)
• Hand-arm vibration (HAV) is vibration transmitted to a person’s hand
and arm when using hand-held power tools, hand-guided machinery
or while holding materials being processed by plant.
• HAV is commonly experienced by people who use jack-hammers,
chainsaws, grinders, drills, riveters and impact wrenches.
• 3 Factors that influence the effect of vibration on the hand
1. Physical Factors
2. Biodynamic Factors
3. Individual Factors

30. 8+9
Physical Factors Biodynamic Factors Individual Factors
Acceleration of vibration
Grip forces - how hard the worker grasps the
vibrating equipment
Operator's control of tool
Frequency of vibration
Surface area, location, and mass of parts of
the hand in contact with the source of
vibration
Ability to change or vary the
work rate of the machine
Duration of exposure each workday
Hardness of the material being contacted by
the hand-held tools, for example metal in
grinding and chipping
Skill and productivity
Years of employment involving
vibration exposure
Position of the hand and arm relative to the
body
Individual susceptibility to
vibration
State of tool maintenance
Texture of handle-soft and compliant versus
rigid material
Smoking and use of drugs.
Exposure to other physical and
chemical agents.
Protective practices and equipment
including gloves, boots, work-rest
periods.
Medical history of injury to fingers and hands,
particularly frostbite
Disease or prior injury to the
fingers or hands

31. Measuring vibration levels
• Measurement of HAV can be difficult and complex
• When workers report symptoms like tingling and numbness after using
vibrating tools it is likely their exposure to HAV is reaching a level
which could lead to Hand-Arm Vibration Syndrome (HAVS)
• This may be an indicator of a HAV problem and controls should be put
in place to eliminate or minimise exposure
• Daily vibration exposure A(8): Exposure to HAV depends on both the
magnitude (intensity) of vibration expressed as acceleration in metres
per second squared (m/s2) and the duration of exposure.
• The daily vibration exposure A(8) for a worker carrying out one process
or operating one tool can be calculated from magnitude and exposure
duration using the equation:

32. 𝐴 𝟖 = 𝒂𝒉𝒗
𝑻
𝑻𝟎
• where:
• 𝑎ℎ𝑣 is the vibration magnitude (in m/s²)
• T is the actual duration of exposure in hours or trigger time
• T0 is the reference duration of eight hours.
• Like vibration magnitude, the daily vibration exposure has units of metres per
second squared (m/s²).
• The duration of exposure or trigger time is the time the hands and arms are
actually exposed to the vibration from the tool or work piece.
• The trigger time is often much shorter than the overall time on the job and is
usually over-estimated by workers.
• The method used for estimating trigger times often depends on whether the
tool usage is continuous or intermittent.
• The value of 𝑎ℎ𝑣 may come from measured data, manufacturer’s information or
other sources like online databases.

33. • If a person is exposed to more than one source of HAV, then partial
vibration exposures are calculated from the magnitude and duration for
each source.
• The overall daily vibration exposure can be calculated from the partial
vibration exposure values using the equation:
𝐴 8 = 𝐴1(8)2+ 𝐴2(8)2+ …
• where A1(8), A2(8) etc. are the partial vibration exposure values for the
different vibration sources.
• An easy way of working out the daily vibration exposure and comparing it
to the exposure action value and exposure limit value is to use the
exposure points system
• This system can be used regardless of the source of the vibration
magnitude.

34. Class of plant Type of plant Vibration magnitude
Road breakers Typical 12 m/s2
Modern tool designs, good operating
conditions and trained operators
5 m/s2
Worst tools and operating conditions 20 m/s2
Demolition
hammers
Modern tools 8 m/s2
Typical 15 m/s2
Worst tools 25 m/s2
Hammer
drills/combi
hammers
Typical 9 m/s2
Best tools and operating conditions 6 m/s2
Worst tools and operating conditions 25 m/s2
Needle scalers Modern tool designs 5-7 m/s2
Older tool designs 10-25 m/s2
Scabblers (hammer
type)
Typical 20-40 m/s2
Angle grinders
(large)
Modern vibration-reduced designs 4 m/s2
Other types 8 m/s2
Angle grinders
(small)
Typical 2-6 m/s2

35. • Exposure Action Value : If daily vibration exposure is likely to exceed
an A(8) of 2.5 m/s2action should be taken to reduce exposure to
below this value.
• Exposure Limit Value: Controls must be put in place to ensure a
worker is not exposed under any circumstances to a daily vibration
exposure A(8) of more than 5.0 m/s2.

36. Hand-Arm Vibration health effects
• Regular and frequent exposure to hand-arm vibration can lead to two
forms of permanent ill health known as:
1. hand-arm vibration syndrome (HAVS)
2. carpal tunnel syndrome (CTS)

37. 1. Hand-arm vibration syndrome (HAVS)
Symptoms and effects of HAVS include:
• Tingling and numbness in the fingers which can result in an inability to do fine
work (eg. assembling small components) or everyday tasks (eg. fastening
buttons)
• Loss of strength in the hands which might affect the ability to do work safely
• Fingers going white (blanching) and becoming red and painful on recovery.
Reducing ability to work in cold or damp conditions, eg outdoors.

38. 2. Carpal tunnel syndrome (CTS)
• Symptoms and effects of CTS can also occur and include:
• Carpal tunnel syndrome (CTS) is a medical condition due to compression of the
median nerve as it travels through the wrist at the carpal tunnel
• Tingling, numbness, pain and weakness in the hand which can interfere with work
and everyday tasks and might affect the ability to do work safely.
• Symptoms typically start gradually and during the night.
• Pain may extend up the arm.

39. (2) Whole-body vibration (WBV)
• Whole-body vibration (WBV) is the vibration and shock felt when
sitting or standing on a vehicle or machine, travelling over rough
ground or along a track, or the vibration when working near powerful
machinery such as a rock crusher.
• Exposure to WBV at low levels is unlikely on its own to cause back
injury, but it can aggravate existing back injuries which may cause
pain.
• Low back pain has been shown to be the leading major cause of
industrial disability in the population under the age of 45 years and
has been linked to whole body vibration exposure.

40. • Exposure to WBV may,
• cause discomfort
• reduce performance
• cause health effects
• Health Effects of WBV:
• The longer a worker is exposed to WBV the greater the risk of health effects and
musculoskeletal disorders.
• The most commonly reported disorder is lower-back pain.
• Long term exposure to WBV may cause:
• neck and shoulder problems
• Disc problem, and early degeneration of the spine.
• Exposure to WBV may contribute to other health effects including:
• cardiovascular, respiratory, neurological, endocrine and metabolic changes, digestive
problems
• reproductive organ damage in both men and women, and
• impairment of vision, balance or both.

41. Controlling Exposure to Vibration
• Anti-Vibration Tools: Tools can be designed or mounted in ways that
help reduce the vibration level. For example, using anti-vibration
chain saws reduces acceleration levels by a factor of about 10, anti-
vibration pneumatic chipping hammers and vibration-damped
pneumatic riveting guns.
• Anti-Vibration Gloves: Anti-vibration gloves are made using a layer of
elastic material. Actual measurements have shown that such gloves
have limited effectiveness.
• Safe Work Practices: Along with using anti-vibration tools and gloves,
workers can reduce the risk of hand-arm vibration syndrome (HAVS)
by following work practices:

42. • Use a minimum strength hand grip that still allows the safe operation of
the tool or process.
• Wear sufficient clothing, including gloves, to keep warm.
• Avoid continuous exposure by taking rest periods.
• Rest the tool on the work piece whenever practical.
• Do not use faulty tools.
• Maintain tools properly. Tools that are worn, blunt or out of alignment
will vibrate more.
• Consult a doctor at the first sign of vibration disease and ask about the
possibility of changing to a job with less exposure.

43. Ventilation

44. • Ventilation is the mechanical system in a building that brings in "fresh"
outdoor air and removes the "contaminated" indoor air.
• In a workplace, ventilation is used to control exposure to airborne
contaminants.
• It is used to remove contaminants such as fumes, dusts, and vapours, in
order to provide a healthy and safe working environment.
• Ventilation can be accomplished by natural means (e.g., opening a
window) or mechanical means (e.g., fans or blowers).
• Industrial systems are designed to move out (exhaust) and bring in
(intake) a specific amount of air at a specific speed (velocity), which
results in the removal of undesirable contaminants.
• Ventilation systems is designed specifically to match to the type of work
and the rate of contaminant release at that workplace.

45. Purpose of Ventilation
• There are four purposes of ventilation:
1. Provide a continuous supply of fresh outside air.
2. Maintain temperature and humidity at comfortable levels.
3. Reduce potential fire or explosion hazards.
4. Remove or dilute airborne contaminants.

46. Parts of Industrial Ventilation
• An industrial ventilation system has two main parts:
1. Fresh air supply system
2. Exhaust system.
• In general, the supply system is a heating, ventilation, and air-
conditioning system (HVAC) and consists of:

47. supply system Exhaust system.
air inlet an "air intake" area
air filtering equipment ducts to move air from one area to another
ducts air cleaning device(s)
heating/cooling equipment fan(s) to bring in outside air and exhaust the indoor
contaminated air
fan discharge stacks.
air distribution registers

48. Categories of ventilation
• Mechanical ventilation refers to any system that uses mechanical
means, such as a fan, to introduce subaerial air to a space. This
includes positive pressure ventilation, exhaust ventilation, and
balanced systems that use both supply and exhaust ventilation.
• Natural ventilation refers to intentionally designed passive methods
of introducing sub aerial to a space without the use of mechanical
systems.

49. • Mixed mode ventilation (or hybrid ventilation) systems use both natural
and mechanical processes.
• Infiltration is the uncontrolled flow of air from outdoors to indoors through
leaks (unplanned openings) in a building envelope.
• When a building design relies on environmentally driven circumstantial
infiltration to maintain indoor air quality, this flow has been referred to as
adventitious ventilation

50. What are the basic types of ventilation systems?
• There are two types of mechanical ventilation systems used in industrial settings:
1. General industrial ventilation
• Reduces the concentration of the air contaminants, or
• Controls the amount of heat that accumulates in hot industrial environments, by
mixing (diluting) the contaminated air with fresh, clean, uncontaminated air.
• This ventilation system is also known as dilution ventilation.
2. Local exhaust
• Ventilation captures contaminants at, or very near, the source and exhausts them
outside

51. What are the main features of dilution ventilation?
• Dilution ventilation supplies and exhausts large amounts of air to and from an
area or building.
• It usually involves large exhaust fans placed in the walls or roof of a building.
• Dilution ventilation controls pollutants generated at a worksite by ventilating the
entire workplace.
• The use of general ventilation distributes pollutants, to some degree, throughout
the entire worksite and could therefore affect persons who are far from the source
of contamination.
• Dilution ventilation can be made more effective if the exhaust fan is located close
to exposed workers and the makeup air is located behind the worker so that the
contaminated air is drawn away from the worker's breathing zone.

53. What are the limitations of dilution ventilation?
1. Does not completely remove contaminants.
2. Cannot be used for highly toxic chemicals.
3. Is not effective for dusts or metal fumes or large amounts of gases or vapours.
4. Requires large amounts of makeup air to be heated or cooled.
5. Is not effective for handling surges of gases or vapours or irregular emissions.
What is local exhaust ventilation?
• Control air contaminants by trapping them at or near the source, in contrast to
dilution ventilation which lets the contaminant spread throughout the workplace.
• Local exhaust is generally a far more effective way of controlling highly toxic
contaminants before they reach the workers' breathing zones.
This type of system is usually the preferred control method if:
• Air contaminants pose serious health risk.
• Large amounts of dusts or fumes are generated.

54. • Increased heating costs from ventilation in cold weather are a concern.
• Emission sources are a few in number.
• Emission sources are near the workers' breathing zones.
• In a general way, a local exhaust system operates similar to a household vacuum
cleaner with the hose as close as possible to the place where dirt would be
created.
What are the components of local exhaust ventilation?
A local exhaust system has five basic elements:
1. The "hood" or opening that captures the contaminant at the source.
2. Ducts that transport the airborne chemicals through the system (exhaust air)
and the air that is recirculated.
3. An air cleaning device that removes the contaminant from the moving air in the
system (not always required).
4. Fans that move the air through the system and discharges the exhaust air
outdoors.
5. An exhaust stack through which the contaminated air is discharged

56. In general, what are limitations of any ventilation system?
• Some limitations include:
1. The systems deteriorate over the years because of contaminant build-up within the
system, especially filters.
2. Require ongoing maintenance.
3. Regular and routine testing is needed to identify problems early and implement
corrective measures.
4. Only qualified persons should make modifications to a ventilation system to make
sure the system continues to work effectively.

57. About make-up air..
• Need to provide enough air to replace the air that is exhausted from the
workplace.
• If enough make-up air is not provided when large volumes of air are exhausted,
the workplace becomes "starved" for air and negative pressure is created.
• Negative pressure in the workplace increases resistance on the ventilation system
causing it to move less air.
• Air will also enter a building through cracks around doors or windows or other
small openings to try to "equal" the rate of air being removed.
• The result is that workers may be exposed to cold air in the winter, and additional
heating costs may occur.

58. How to figure out –ve pressure inside room ?
• Open the door about 3 millimeters and hold a smoke tube (or another object that
releases smoke) in front of the opening.
1. If the smoke is drawn into the room, the room is under negative pressure.
2. If the smoke is pushed away from the room, the room is under positive
pressure.
3. If the smoke raises straight into the air, then the pressure in the room is the
same as the outside pressure.
• Open a door that pushes towards outside.
1. If you have to pull (or push from inside) hard to open the door, the building is
under negative pressure (the outside pressure is higher than inside, and forces the
door shut)

59. TEMPERATURE
• Extremes of temperature, or thermal stress, affect the amount of work people
can do and the manner in which they do it. In industry, the problem is more often
high temperatures rather than low temperatures.
• The body continuously produces heat through its metabolic processes. Because
the body processes are designed to operate only within a very narrow range of
temperature, the body must dissipate this heat as rapidly as it is produced if it is
to function efficiently
The Body's Responses to Heat
• Dehydration is a common concern when working in a hot environment. It is
caused by failure to replace the salt and water lost through perspiration.
Although perspiring helps the body cool, it is necessary to replace lost fluid and
salt.

60. • Cool, but not cold, water should be provided in a location convenient to workers.
Because the feeling of thirst may not be enough to ensure adequate water intake,
workers in hot environments should be encouraged to drink at least one cup per
hour. Too much water (more than two cups) should not be taken at one time
since workers may develop abdominal cramps.
• Most people consume enough salt as table salt and as naturally occurring salt in
foods. Fruit and vegetable juices can be good sources of natural salt. Encourage
workers on salt-restricted diets to discuss salt needs with their doctor. Salt tablets
should only be taken on a doctor’s advice.

61. Heat-Related Illnesses Symptoms, Prevention and Treatment

63. Factors Contributing to Heat-Related Illnesses
• Lack of acclimatization – the body has not had enough time to adjust, or other
factors prevent the body from adjusting to the heat
• General state of health – the following medical conditions may be a factor in
causing heat illness or may be aggravated by heat:
a) Skin disorders may limit sweating (ex: dermatitis, when aggravated by
heat/moisture).
b) Heart and lung diseases may limit ability to cope with heat and may be
aggravated by it.
c) Diabetes, poorly controlled, may contribute to dehydration and may be
aggravated by excessive heat.
d) Diarrhea may contribute to dehydration.
e) Obesity requires increased energy to move around and the extra insulation
reduces heat loss – both contribute to the body's overall heat gain.

64. • Medication/drugs – can affect the body's responses to heat and may affect
acclimatization. Different medications/drugs may affect different parts of the
body:
a) the brain's thermostat is affected by ASA, phenothiazines
b) the sweating function is affected by pilocarpine, and anticholinergic drugs such
as hyoscine
c) the circulatory system is affected by antihypertensives, antiarrhythmics,
diuretics, alcohol, street drugs
d) the metabolic rate is affected by thyroxin, alcohol, street drugs

65. Acclimatization
• Acclimatization is a gradual process in which the body becomes accustomed to
temperature extremes.
• During initial exposures to a hot environment, workers often feel very tired,
irritable and too hot. Body temperatures often rise. After repeated exposures,
these symptoms decrease or disappear. When this occurs, a person is considered
acclimatized. In the same way that many factors may lead to heat illness, there are
differences in people that affect the rate at which they acclimatize.
Measurement of Occupational Heat Exposure
• The Workplace Safety and Health Act or regulations do not specify a maximum
temperature above which work must stop. Rather, the combination of
environmental conditions must be measured and evaluated against a set of
exposure limits recommended by the American Conference of Governmental
Industrial Hygienists (ACGIH).

66. • To measure occupational heat exposure, combine the environmental factors that
contribute to heat load, as discussed earlier. The most common method involves
the wet bulb globe thermometer (WBGT) or a direct-reading meter, available
commercially. These instruments calculate air temperature, air movement,
radiant heat and evaporation, indoors or out.
• WBGT readings are widely used to estimate the effect of temperature, humidity
and solar radiation on humans over time

67. The WBGT is composed of three separate temperatures:
1. The air (shade) temperature (Tdb) consists of a thermometer shielded from the radiation.
It is the standard temperature normally given in weather observations and forecasts.
2. The natural wet-bulb temperature (Tnwb) is measured by a thermometer with its bulb
covered with a wet cotton wick. The cotton wick is always wet, allowing continuous
evaporative cooling of the thermometer’s bulb, simulating the evaporation of sweat. This
temperature reading represents the effect of radiation, humidity and wind.
3. The black globe thermometer (Tg) consists of a black globe with a thermometer located in
the center. This temperature reading represents the effects of wind and solar radiant heat.
WBGT values are calculated as follows:
• With direct exposure to sunlight:
WBGT out = 0.7 Tnwb + 0.2 Tg + 0.1 Tdb
• Without direct exposure to the sun:
WBGT in = 0.7 Tnwb + 0.3 Tg

68. Heat Exposure Limits
The allowable work/rest to prevent heat stress is shown in Table 4.4 and is adjusted for light,
moderate, or heavy work. Recommendations are made for rest breaks when these
temperatures are exceeded. See Table 4.5 for examples of what is meant by these
workloads, and for the recommended work-rest schedule when the WBGT temperatures
increase.

70. The values in Table 4.4 are based on healthy, acclimatized workers wearing one layer of
customary work clothing. Water-vapour-impermeable, air-impermeable, thermally
insulating clothing, multiple layers of clothing and encapsulating suits severely restrict heat
removal. Variations from the customary clothing require modification of the TLV. See Table
4.6 for suggested modifications.

71. Prevention and Control Measures
The risk of heat-related illnesses can be reduced by preventive and control
measures, including:
1. Engineering controls to provide a cooler workplace
2. Administrative controls to reduce exposure and recognize symptoms of heat-
related illness
3. Personal protective equipment, when necessary, to further limit exposure.
Engineering Controls
Engineering controls are the most effective means of reducing occupational heat
exposure, including:
• planning during the workplace construction if a hot environment is anticipated
• shielding the radiant heat at the source through insulation and reflective barriers

72. • exhausting heat and water-vapour (steam) to the outside
• reducing temperature and humidity through ventilation or air-conditioning
• providing cooled observation booths or air-conditioned rest areas
• increasing general air movement if temperature is less than skin temperature
(approximately 36 degrees C)
• reducing air movement if air temperature is greater than skin temperature
• reducing physical exertion by changing processes or using machines designed to
assist

73. Administrative Controls
Administrative controls like these are the easiest to put in place, for or by the
worker:
• apply a work schedule to allow for heat acclimatization
• increase frequency and length of rest breaks
• schedule hot jobs during cooler times of day
• provide cool drinking water near the work location and encourage workers to
drink even if not feeling thirsty
• slow down work pace or assign additional workers to decrease workload

74. • allow for self-limitation of exposures and encourage co-workers to observe signs
and symptoms of heat stress in each other
• provide workers with accurate written and verbal instructions, frequent training
programs and other information on heat stress
• consider requiring that, as a condition of hiring, prospective employees provide
medical evidence that they are not susceptible to systemic heat related illness
• use air-conditioned rest areas

75. Personal Protective Equipment
Where engineering or administrative controls are not feasible or practical,
occasional use of personal protective equipment may be necessary, including:
• wear insulated or cooled clothing for short-term exposure such as maintenance
jobs
• wear clothing that allows free movement of airflow
• wear heat reflective clothing near heat sources such as a hot furnace
• wear light-filtering eye protection when work involves hot objects such as molten
metals
• use sunscreen and sun block when working outdoors
• wear a hat and light clothing to protect skin when working in the sun

76. Lighting
• Lighting or illumination is the deliberate use of light to achieve a practical or
aesthetic effect.
• Lighting at work is very important to the health and safety of everyone using the
workplace. The quicker and easier it is to see a hazard, the more easily it is avoided.
The types of hazard present at work therefore determine the lighting requirements
for safe operation.
• Poor lighting can not only affect the health of people at work causing symptoms like
eyestrain, migraine and headaches, but it is also linked to Sick Building Syndrome in
new and refurbished buildings. Symptoms of this include headaches, lethargy,
irritability and poor concentration

77. • Good lighting in the workplace promotes:
1. a reduced risk of occupational accidents and health problems;
2. better concentration and accuracy in work;
3. a brighter, cleaner workplace resulting in a more active, cheerful environment;
4. improved work performance;
5. better visibility, improved accuracy and increased work speed enhancing
production

78. Sources of Lighting
Daylight: How much daylight reaches inside a building depends on the architecture of the
building (does the building have windows; how big; how are they oriented?), the amount
and direction of sunlight, cloud cover, local terrain, and the season. The cleanliness of the
windows is important as well. The amount of daylight entering the workplace can be
controlled with tinted glass, window blinds, curtains, and awnings. Daylight is desirable in
the workplace providing it does not cause glare or make the work area too bright.
Remember, not enough light can also be a problem so even in workplaces where daylight is
available, it is essential to have a good electric lighting system.
Electric Lighting: The amount of light, the colour of the light itself and the colour that
objects appear vary with the type of electric lighting. The lighting must match the
workplace and the task. The following are common types of bulbs.

79. Basic Types of Artificial Lighting
There are three basic types of lighting:
• General.
• Localized-general
• Local (or task).
General lighting provides fairly uniform lighting. An example would be ceiling fixtures that
light up large areas.

80. • Localized-general lighting uses overhead fixtures in addition to ceiling fixtures to increase
lighting levels for particular tasks.
• Local (or task) lighting increases light levels over the work and immediate surroundings.
Local lighting often allows the user to adjust and control lighting and provides flexibility
for each user.

81. Types of light fixtures
• The complete lighting unit (also called the light fixture) controls and distributes the light.
(Light fixtures are often referred to as "luminaires" in technical publications.) Various types of
light fixtures are designed to distribute light in different ways. These fixtures are known as:
1) Direct. 2) Direct-indirect. 3) Indirect. 4) Shielded (various types).
• No single type of light fixture is appropriate in every situation. The amount and quality of
lighting required for a particular workstation or task will determine which light fixture is most
suitable.
1) Direct light fixtures project 90 to 100 percent of their light
downward toward the work area. Direct lighting tends to
create shadows.
2) Direct-indirect light fixtures distribute light equally upward and
downward. They reflect light off the ceiling and other room surfaces.
Little light is emitted horizontally meaning direct glare is often reduced.
They are usually used in "clean" manufacturing areas.

82. Indirect light fixtures distribute 90 to 100 percent of the light upward.
The ceiling and upper walls must be clean and highly reflective to allow
the light to reach the work area. They provide the most even illumination
of all the types of fixtures and the least direct glare. Indirect light fixtures
are usually used in offices.

83. Shielded light fixtures use diffusers, lenses and louvers to cover bulbs from
direct view; therefore, helping to prevent glare and distribute light.
• Diffusers are translucent or semi-transparent (see-through) covers made
usually of glass or plastic. They are used on the bottom or sides of light
fixtures to control brightness.
• Lenses are clear or transparent glass, or plastic covers. The lens design
incorporates prisms and flutes to distribute light in specific ways
• Louvers are baffles that shield the bulb from
view and reflect light. The baffles can be
contoured to control light and decrease brightness.
Parabolic louvers are specially shaped grids that
concentrate and distribute light.

84. Seven Principles of Good Illumination
1. Make Good Use of Natural Light
2. Give Priority to High Luminous Efficiency Lights
3. Different Lighting Solutions for Different Heights
4. Select Lights with Right color rendering index (CRI) and Color Temperature
5. Make Sure There’s sufficient light Intensity(lux)
6. Control the Glare
7. Lighting for Special Production areas should be selected appropriately