002 identifying and evaluating confined space hazards

7/30/2019 002 Identifying and Evaluating Confined Space Hazards

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IDENTIFYING AND EVALUATIINGCONFINED SPACE HAZARDS


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CLASSIFICATION

There are two main categories of confined spaces, namely:

permit-required confined spaces

non-permit-required confined spaces

Not all confined spaces will be considered permit-required

confined spaces and being able to identify the difference between

the two is important.


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NON PERMIT REQUIRING

A Non-Permit Confined Space is a confined space that does notusually contain, nor usually has the potential to contain, any hazard

capable of causing death or serious physical harm.

Examples of non-permit required confined spaces might include the

following: interiors of HVAC units,

certain air plenums and pipe chases,

attics,

walk-in freezers or refrigerators, and

building crawl spaces.


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PERMIT REQUIRING SPACE

A Permit Required Confined Space means a confined space that hasone or more of the following characteristics:

Contains or has a potential to contain a hazardousatmosphere,

Contains a material that has the potential for engulfing anentrant,

Contains any other serious safety or health hazard.

Has an internal configuration such that an entrant could betrapped or asphyxiated by inwardly converging walls or by a floorwhich slopes downward and tapers to a smaller cross-section.


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PERMIT REQUIRING SPACE

Examples of serious safety or health hazards might include thefollowing:

Fall hazards

Unguarded machinery

Extreme heat or cold Steam pipes or chemical lines

Hazardous noise levels

Electrical hazards

Presence of asbestos

Potentially hazardous levels of dust (such as might occur at a

Feed Mill)


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PHASE 1

IDENTIFYING / RECORDING


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IDENTIFYING / RECORDING

Initial surveys are conducted to identify all of the

confined spaces at the site and to prepare an inventory

list of these spaces.

The spaces on the list will then be classified according

to type. With the ready availability of digital photography, it is

often beneficial to include photos with the hazard

assessment.


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PHASE 2

ASSESSMENT


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CONFINED SPACE HAZARDS

Analysis of typical causes of fatalities

47% Air (Oxygen, Gases, Vapors)

21% Drowning (Engulfment)

19% Toxic (Liquids, Vapors, etc above PEL

10% Blunt Force Trauma 2% Electrocution (Mostly due to objects the victim took in

with them)

1% Burns


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HAZARD CATEGORIES

The main confined-space hazards can be grouped into the followingcategories:

Oxygen-deficient atmospheres

Flammable atmospheres Toxic atmospheres

Mechanical and physical hazards
http://www.pp.okstate.edu/ehs/manuals/CONFINED/Sec_2.htm


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HAZARDOUS ATMOSPHERES

Asphyxiating atmospheres

Flammable atmospheres

Toxic atmospheres


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OXYGEN DEFICIENT ATMOSPHERE

"Oxygen-deficient atmosphere" means an atmosphere

containing less than 19.5 percent oxygen by volume

Note: Exposures to atmospheres containing 12% or less oxygen

will bring about unconsciousness without warning and so quicklythat individuals cannot help or protect themselves


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Oxygen deficiency can be caused by:displacement(by another gas within the confined space), or

consumption. There are a number of processes that consume

oxygen in a confined space:

Oxygen is consumed during combustion of flammable

materials, as in welding, cutting, or brazing.

A more subtle consumption of oxygen occurs during

bacterial action, as in the fermentation process.


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Oxygen can also be consumed during chemical reactions suchas in the formation of rust on the exposed surfaces of a confined

space.

The number of people working in a confined space and the

amount of physical activity can also influence oxygen consumption.


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NITROGEN (N2)

Colorless, odorless inert gas

Slightly lighter than air

Vapor density (0.97)

May displace oxygen and cause asphyxiation


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METHANE (CH4)

Natural, marsh or swamp gas

Colorless, odorless, flammable gas

Lighter than air

Vapor Density (0.6)

Toxic? Lower Exposure Limit (LEL)= 5%;

Upper Exposure Limit (UEL) = 15%


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CARBON MONOXIDE (CO)

Colorless, odorless gas

Slightly lighter than air

Vapor Density (0.97)

Chemical asphyxiant

Primary source: incomplete combustion of organic material Gasoline-fueled combustion engines


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CARBON MONOXIDE (CO)

Permissible Exposure Limit (PEL) = 50 ppm

Threshold Limit Values (TLV):

- Time Weighted Average (TWA) = 25 ppm

- Respiratory Exposure Limit (REL) = 35 ppm

- Short Term Exposure Limit = 200 ppm

Lower Exposure Limit (LEL) = 12.5%;

Upper Exposure Limit (UEL) = 74.2%


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HYDROGEN SULPHIDE (H2S)

Sewer gas, stink gas (rotten eggs)

Produce olfactory fatigue (loss of sense of smell)

Odor threshold: 0.02-0.2 ppm

Colorless, flammable gas

Lower Exposure Limit (LEL) = 4.3% Upper Exposure Limit (UEL) = 46.0%

Heavier than air

Vapor density (1.18)


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HYDROGEN SULPHIDE (H2S)

Permissible Exposure Limit = 20 ppm50 ppm-Peak (10 min once)

Threshold Limit Values (TLV):

- Time Weighted Average (TWA) = 10 ppm

- Respiratory Exposure Limit (REL) = 10 ppm (10 min)- Short Term Exposure Limit = 15ppm


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ATMOSPHERIC HAZARDS

Definitions

Vapor Density- The weight of a flammable vapor compared

to air (Air=1).

Vapors with a high density are more dangerous and requirebetter ventilation because they tend to flow along the floor

and collect in low spots.


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ATMOSPHERIC HAZARDS

Definitions

PEL - The Permissible Exposure Limit of a gas or vapor accordingto formal standards, expressed in parts of vapor per millionparts (ppm) of contaminated air.

Many flammable and combustible liquids present an inhalationas well as a fire hazard.

HOW HAZARDS OCCUR


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HOW HAZARDS OCCUR

1. Previously stored products / chemicals

2. Manufacturing processes

3. Operations/work being performed

4. Adjacent areas


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GENERAL HAZARDS

Electrical

Mechanical

Engulfment

Entrapment


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ELECTRICAL INJURIES

The voltage of the circuit

The resistance of the persons body

The flow of current through the body

The circuit path through the body


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ENGULFMENT

" Engulfment" means the surrounding and effective capture of a personby a liquid or finely-divided (flowable) solid substance that can be

aspirated to cause death by filling or plugging the respiratory system or

that can exert enough force on the body to cause death by strangulation,

constriction, or crushing.


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MECHANICAL/ENTRAPMENT

Agitators Augers

Unguarded chains

Unguarded pulleys

Unguarded rotating blades

Unguarded belts Unguarded fans

Moving parts

Rotating parts


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PHYSICAL HAZARDS

Thermal effects

Noise

Vibration

Structural

Corrosives

THERMAL EFFECTS


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THERMAL EFFECTS

Heat stress

Cold stress

NOISE HAZARDS


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NOISE HAZARDS

Distraction

Physical damage to ear

Interference with communications

Stress

OTHER HAZARDS


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OTHER HAZARDS

Unstable or dangerous work surfaces

Falling objects

Insects or animals

Biological


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ASSESSMENT

APPROACH

DEFINITION


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DEFINITION

HAZARD is a condition or practice which has the potential to causeharm

e.g., substances, methods of work, dangerous parts of machines

HAZARD IDENTIFICATION


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HAZARD IDENTIFICATION

The hazard identification process should consider the following:

all aspects of the work/machinery etc. under normal

circumstances

possible non-routine operation/work situations, or

effect of interruptions / changes to the work/operation.

all persons who may be affected by the activities

(highlighting persons who are particularly affected)

existing control measures

DEFINITION


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DEFINITION

RISK is the likelihood that the harm from a particular hazard will

occur

The chance of harm or loss

The extent of risk depends on the severity of the harm, and alsothe number of people affected


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RISK

CONSEQUENCE

(Consequence Analysis)

FREQUENCY

(Frequency Analysis)

PROBABILITYEXPOSURE

RISK EVALUATION


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RISK EVALUATION

Risk evaluation uses values in order to calculate the riskfactor. This would usually include values based on:

measurement ofconsequence

measurement ofexposure

measurement ofprobability

REVIEW


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REVIEW

Surveys and hazard assessments should be updated periodically. A general review of all items should be conducted at least

annually.

If changes occur in the facility or processes, the affected

spaces need to be reassessed immediately.

Reports of issues from entry crews may also provide

warning that a space needs to be reevaluated e.g. if the crew

discovers a hazardous atmosphere in a space that does not usually

contain one, the source of the hazard should be determined and

the hazard assessment revised if necessary.

002 identifying and evaluating confined space hazards

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