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The Working Environment
• The workplace environment.
• Fire prevention and building design.
• Explosion radiation and hazardous material
1

2
The Work Place Environment
• When studying the workplace environment the
following topics must be taken into consideration:
– Atmospheric conditions
– Walking and standing surfaces (tutorial)
– Egress and life safety (tutorial)
– Noise and noise control
– Fire prevention and suppression
– Explosion
– Radiation
– Hazardous materials

3
Atmospheric Conditions
• Controlling elements:
– Temperature
– Humidity
– Air cleanliness
• The desired effect of the above elements
differs from one region to another.

4
Controlling Temperature and Humidity
• General comfortable ranges:
– [25 – 30]oC at 0% humidity
– [23 – 27]0C at 80% humidity
• Tools, such as the Psychometric Chart, are
used as a design aid.

Psychrometric chart: Example 1
• Given: T = 25°C , Tw =20°C
• Required: (a) RH, (b) Tdp, (c) HR, (d) v, (e) h
13

15
Controlling Air Cleanliness
• Cleanliness of the air refers to:
– Sufficient percentage of Oxygen.
– Absence of harmful elements.
– Clean air contains 21% oxygen with no toxic
matter.
– Minimum permissible percentage of oxygen:16-
18%, lest unclear thinking and slow muscular
activities should occur.

16
Toxic Materials in Air
• Threshold limit value (TLV): Maximum
permissible limit of exposure to toxic material
in ppm (part per million parts of air (mg/mm3)
• Toxic materials have cumulative effects.

20
Maintaining Air Cleanliness
• Making air acceptably free of any harmful
substances to human health and comfort.
• Best way to achieve: avoid generation of
foreign matter in the first place.
• If not feasible?
– Use PPE (X)
– Use ventilation (√)

21
Ventilation Methods
• Local exhaust ventilation:
– Catch foreign matter as close as possible to the point of
generation. (efficient, foreign matter is collected before
people breath it).
• General ventilation:
– Exhaust the air from the entire room and replace it with
clean air. (expensive, used when foreign matter is
widespread, can not be used when the foreign matter is
toxic, needs equipment to supply fresh air)
• Both methods are ways of diluting the concentration
of foreign matter since neither will result in capturing
100% of it.

24
Components of Local Exhaust Systems
• Hood
• Ducts
• Fan
• Discharge
• Air cleaner (optional according to application )

25
Hood
• It is the most critical part as it is the inlet to
the system
• Choice of the hood type should be based on:
– Toxicity of contaminant
– Specific gravity of contaminant
– Size and area of generation
– Air disturbance in this area

27
Other Hood Types
Canopy Down draft
Enclosed Point collector
Rear slotted (Draw them)

28
Cleaning devices
• Used to draw air into the duct, clean it, and discharge
it back.
• Types of cleaning devices:
– Mechanical separators
– Filtration devices
– Wet collectors
– Electrostatic
– precipitators
– Gas absorbers
– Combustion incinerators

29
Mechanical Separators
• Draw:

30
Fire Prevention
Egress and Life Safety

31
Exit Routes, Emergency Action Plans, Fire
Prevention Plans,
and Fire Protection

32
Introduction
• Fires and explosions kill more than
200 and injure more than 5,000
workers each year
• There is a long and tragic history of
workplace fires caused by problems
with fire exits and extinguishing
systems
• OSHA requires employers to provide
proper exits, fire fighting equipment,
and employee training to prevent fire
deaths and injuries in the workplace

33
Exit Route
• A continuous and
unobstructed path of exit
travel from any point within
a workplace to a place of
safety (including refuge
areas)*
• Consists of three parts:
– Exit access
– Exit
– Exit discharge

34
Refuge Area
A refuge area is:
– A space along an exit route protected from fire by
a barrier with at least a 1-hour fire resistance
rating; or
– A floor with at least 2 spaces, separated from
each other by smoke-resistant partitions, in a
building protected by an approved automatic
sprinkler system

35
Exit Routes
Basic Requirements
• Exit routes must be permanent and there
must be enough exits in the proper
arrangement for quick escape
• Exits must be separated by fire-resistant
materials
• Openings into an exit must be limited to
those necessary to allow access to the
exit or to the exit discharge
• An opening into an exit must be
protected by an approved self-closing fire
door that remains closed or automatically
closes in an emergency

36
Exit Discharge
• Each exit discharge must lead directly
outside or to a street, walkway, refuge
area, public way, or open space with
access to the outside that is large
enough to accommodate all building
occupants likely to use the exit route
• Exit stairs that continue beyond the
level on which the exit discharge is
located must be interrupted on that
level by doors, partitions, or other
effective means that clearly indicate
the direction of travel to the exit
discharge

37
Exit Doors Must Be Unlocked
• Must be able to open from the
inside at all times without keys,
tools, or special knowledge
• Must be free of any device or
alarm that could restrict
emergency use if the device or
alarm fails
• May be locked from the inside only Locked and
blocked exit

38
Side-Hinged Exit Door
• Must be used to connect any room to an exit
route
• A door that connects any room to an exit route
must swing out in the direction of exit travel if
the room is designed to be occupied by more
than 50 people or contains high hazard
contents
• High hazard contents are those which are liable
to burn with extreme rapidity or which may
produce poisonous fumes or explosions in a
fire. Examples include flammable chemicals
and grain.

39
Minimize Danger to Employees
• Exit routes must be free and
unobstructed
• Keep exit routes free of explosive
or highly flammable materials
• Arrange exit routes so that
employees will not have to travel
toward a high hazard area, unless
it is effectively shielded
• Emergency safeguards (e.g.,
sprinkler systems, alarm systems,
fire doors, exit lighting) must be in
proper working order at all times
Obstructed
exit route

40
Exit Marking
• Each exit must be clearly
visible and marked with
an “Exit” sign
• Each exit route door must
be free of decorations or
signs that obscure the
visibility of the door

41
Exit Marking (cont’d)
• If the direction of travel to
the exit or exit discharge is
not immediately
apparent, signs must be
posted along the exit
access indicating direction
to the nearest exit
• The line-of-sight to an exit
sign must clearly be visible
at all times

42
Emergency Action Plan
• Describes actions that must be
taken to ensure employee safety
in emergencies
• Includes floor plans or maps which
show emergency escape routes
• Tells employees what actions to
take in emergency situations
• Covers reasonably expected
emergencies, such as fires,
explosions, toxic chemical
releases, hurricanes, tornadoes,
blizzards, and floods

43
Fire Prevention Plan
The plan must include:
• A list of the major fire hazards and handling, storage,
and control procedures
• Names or job titles of persons responsible for
maintenance of equipment and systems to prevent or
control ignitions or fires
• Names or job titles of persons responsible for control
of fuel source hazards
• Training for all employees who have responsibilities in
the plan

44
Portable Fire Extinguishers
If portable fire extinguishers are
provided for employee use, the
employer must mount, locate and
identify them so workers can
access them without subjecting
themselves to possible injury.
Blocked extinguisher

45
Extinguisher Classification
• Class A – ordinary combustibles (wood,
cloth, paper)
• Class B – flammable liquids, gases, greases
• Class C – energized electrical equipment
• Class D – combustible metals
A B C D
Ordinary
Combustibles
Combustible
Metals
Flammable
Liquids
Electrical
Equipment

46
The Realm of Growth of Flame

47
Maintaining Portable Fire Extinguishers
• Must maintain in a fully charged and
operable condition
• Must keep in their designated places
at all times except during use
• Must conduct an annual maintenance
check
• Must record the annual maintenance
date and retain this record for one
year after the last entry or the life of
the shell, whichever is less

48
Explosion, Radiation and Hazardous
Materials

49
EXPLOSION
• Characteristics of an explosion
• Causes of explosion
• Effect of rate of flame spread
• Overpressure
• Explosives and explosive substances
• Classes of explosives
• Handling explosive substances
• Handling Facility design
• Building design

50
Characteristics of an Explosion
• An explosion begins with the ignition of a fuel
that burns very rapidly, producing a large and
sudden release of gas.
• When a container bursts from increased
internal pressure. The sudden release of
pressure is referred to as an explosion.

51
Explosive substances and explosives
• Explosive substances is a term used to
describe the materials that are capable of
causing an unwanted explosion.
• Explosives are those materials designed to
release large overpressures when detonated

52
Materials that should be explosives in
nature
• Chlorine radicals
• Nitrogen radicals
• Peroxides
• Ethers
• Bromates and iodates
• Permanganates and chromates
• Benzoates
• Butane and propane
• Nitroglycerin
• trinitrotoluene

53
Explosive Materials classes and signs
• Forbidden or no acceptable: not to be carried
on common transporters.
• Class A: detonating, highly explosive
substances.
• Class B: flammable hazard, they function by
rapid combustion rather than detonation,
eg:fireworks.
• Class C: minimum hazard, eg. Small arms
ammunition.

56
Handling explosive substances
• Explosive materials are prone to detonate
with increased temperature, pressure or
vibration.
• They must be handled and stored in
ventilated, free from vibration areas and.
• Keep materials with small quantities in
separate jars.
• Clearly label the containers.

59
RADIATION
• Characteristics of radiation
• Symbols and signs
• Exposure standards
• Controlling exposures

60
Characteristics of radiation
• The NFPA defined Radioactive materials as
substances that spontaneously decay, emitting
energetic rays or particles in the process
• Thus radiation is a form of energy, natural or man
made.
• The electromagnetic spectrum covers those forms of
energy with wave length of approx. 10-14 meters to
105 meters that corresponds to frequencies of
approx. 1022 hertz to approx. 1000 hertz.

61
The Electromagnetic Spectrum

62
The Electromagnetic Spectrum (cont.)
 All forms of radiation travel at the speed of light but
at different frequencies.
 The wavelength is inversely proportional to the
frequency

64
• Several standards have been published to restrict
exposure of workers to radiations
• Exposure limits are expressed in Rems
• Rems refers the röntgen equivalent man it is an
obsolete unit of radiation dose that liberates positive
and negative charges of 2.58×10-4 coulombs per
kilogram of air. The corresponding SI derived unit is
the sievert.
• A man can withstand up to 5 rems (0.5 rem from
nature and a max of 4.5 rems exposure)
Exposure Standards (cont.)

65
Controlling exposures
• Manny types of radiations cannot be seen.
• Visible radiations are generally not identifiable
• Corrective measures:
– Try to eliminate them
– Concentrate on RF (radio frequency) radiations the most
common in industry:
• Use grounded electrical shielding around the equipment with RF,
to carry the charge to the ground.
• Keep parts of the body away as you can
• Turn off equipment when not in use
• Use PPE
• Use signs

66
• Use distance as a protective measure:
– without source of energy, most radioactive activities decay.
– A radioactive material half-time: is the length of time a
particular source takes to decay 50% of its initial strength
or power. This is expressed by: Y2 = Y1 *(1/d2)
• Y1 is the exposure at the initial point
• Y2 is the exposure at a removed distance
• D is the ratio of distances of points 2 and 1
– Example: a worker receives 100 mR/hr at a distance of 2
meters from the source of radiation, at 6 metres he will
receive:
• Y2 = 100*(1/(6/2)2) = 11.1 mR/hr
Controlling exposures (cont.)

67
Controlling exposures (cont.)
• Use radiations at the lowest
energy levels.
• Use barriers :alpha particles
have very little ability to
penetrate but do much
damage to cells, Beta
particles penetrate easily
are not as destructive as
alpha particles.
• X-rays, gamma rays and
neutrons penetrate easily
Thickness of shield
(mms)
Paper/
cloth
Al Lead
Alpha 0.4 0.4 0.13
Beta - 5.3 1.4
X-rays - 70 7.6
Gamm
a rays
- 70 7.6

68
HAZARDOUS MATERIALS
• Exposure to poisons
• Signs
• Permissible concentration and exposure
duration
• Disposal of hazardous waste

69
Exposure to poisons
• To determine the harmful effect of some toxic
materials test are conducted on small animals.
• The lethal dose LD50.:is a dose of a given substance
which is expected to kill 50% of the test animals.
• The lethat concentration LC50 is used if the
substance is ingested with the air. It is the
concentration in parts per million expected to kill
50% of the test animals
• Toxic materials may be solid liquid or gaseous (review
exhaust systems).

70
Signs
• RED (on top of the diamond)
denotes flammability
• Yellow (to the right) indicates
chemical reactivity
– often "WATER REACTIVE"
dangers
– Sodium metal, if present,
would require a 4 rating.
• BLUE (to the left) represents
toxicity,
• WHITE (bottom) signifies specific
hazards, e.g. oxidizers, acids,
bases, or corrosive
Biomedical
materials
Corrosive
materials
Chemicals
Diamonds

71
Disposal of hazardous waste

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