Education

1. Hazards of Confined Spaces

2. Hazards of Confined Spaces
INSTRUCTIONAL GOAL
The participant till understand the various hazards
associated with confined space entries and the need
to monitor permit required confined spaces.

3. ENABLING OBJECTIVES
 Identify various confined space hazards.
 Explain the sequence of confined space atmospheric
monitoring
 List some qualities of a good monitoring device.
 Describe the acceptable atmospheric conditions for
entry.

4. Hazards of Confined Spaces
 Atmospheric Hazards:
 Oxygen Deficient / Enriched
 Flammable Atmosphere
 Toxic Atmosphere

5. Oxygen Deficient Atmospheres
Purging
Natural processes
Gas displacement
Oxygen absorption

7. < Less than 19.5 %
> Greater than 23.5 %
OSHA Action Limit for
Oxygen Concentration

8. Effect of Oxygen Deficiency
19.5% Minimum permissible oxygen level
16 – 19% Decreased ability to work strenuously.
May impair coordination and induce
early symptoms in person with
coronary, pulmonary, or circulatory
problems.
13 – 16% Respiration increases in exertion, pulse
up, impaired coordination, perception,
judgment.

9. Effects of Oxygen Deficiency
10-13% Respiration farther increases in rate and
depth, poor judgment, blue lips.
8 – 10% Mental Failure, Fainting, Unconsciousness,
ashen face, blueness lips nausea, and
vomiting.
6 – 8% 8 minutes, 100% fatal,
6 minutes, 50% Fatal
4 minutes, recovery with treatment
<6% Coma in 1 minute, convulsions, death.

10. Vapor Density
Oxygen levels can be lowered by gas displacement.
Vapor density is a measure of how dense a gas is as
compared to an equal volume of air.

11. Vapor Density
Vapor Densities of Selected Gases and Vapors:
Methane 0.55
Carbon Monoxide 0.96
Hydrogen Sulfide 1.19
Freon (R-12) 4.30

12. Purging
Purging a tank or vessel is a
common industrial practice.
By introducing an inert (non-
reactive) gas into a tank,
flammable vapors and oxygen
will be forced out of the tank.

13. Common Flammable Gases in
Confined Spaces
 Hydrogen Sulfide
 Methane
 Solvent Vapors
 Gasoline
 Paint Vapors

14. Flammable Gases –
The Fire Triangle

15. Flammable Atmospheres –
Flammable Range
The lower explosive limit (LEL) or
lower Flammable limit (LFL) is the
minimum concentration of gas or
vapor in air below which the
substance will not burn.

16. Flammable Atmospheres –
Flammable Range
The upper explosive limit
(UEL) or Upper Flammable
limit (UFL) is the maximum
concentration of gas or
vapor above which the
substance will not burn.

17. FLAMMABLE RANGE
Normal Oxygen Level 21% in air
LEL and UEL will change as oxygen level changes.

18. FLAMMABLE RANGE
Flammable Range of Selected Gases and Vapors
Flammable Vapor or Gas LEL UEL
 Acetylene 2.5% 100.0%
 Carbon Monoxide 12.5% 74.0%
 Gasoline 1.3% 7.1%
 Hydrogen Sulfide 4.3% 46.0%
 Natural Gas 3.8% 17.0%
 Propane 4.5% 14.5%

19. Natural Production of
Flammable Atmospheres
Natural Decay Processes
Seepage of Flammable Liquids Underground
Previous Contents were Flammable
Intentional Dumping of Flammable Liquids

20. Greater than 10% of LEL
for Gases
Vision distance < less than
5 Feet for airborne dust
OSHA Action Limit for Flammable
Gases & Dusts

21. Production of Flammable
Atmospheres by Entrants
Hot work vaporizes tank coatings
Spray paints or coatings
Leaks from torch gases

22. Cleaning
Procedures and processes used
to clean the inside of a confined
space are reviewed and
authorized by the qualified
person.
Initial cleaning is done from
outside the tank if at all possible.

23. Operations in the spaces
 Welding
 Painting
Inerting operations,
carbon dioxide, nitrogen
Chemical Hazards in Confined Spaces

24. Chemical Hazards in Confined Spaces
Chemical reactions from:
 Manufacturing process
 Products Stored
 Drying Paints
 Oxidation / reduction reactions
 Cleaning with acids or solvents
 Rusting of metal
 Curing of concrete
 Rotting / decomposing / fermentation

25. Toxicity
Defined as the degree to
which a chemical or biological
substance has a harmful
effect on the human body.

26. Toxicity
Effect of a toxic substance is dependent upon:
Dose
Toxicity of the Substance

27. Human Toxicology Routes of Entry
 Inhalation
 Eye and skin contact
 Ingestion
 Injection

28. Hazard Assessment
 PEL: (Permissible Exposure Limit) This is the lower limit of hazard for a
particular toxin. Any concentration less than the PEL is considered to be safe
at least for acute exposure. Any concentration greater than the PEL required
some type of preventative action prior to entry. PEL is an OSHA term. TLV
(Threshold Limit Value) is the NIOSH equivalent to PEL.
 TWA: (Time-Waited Average) This is a dose measurement which is more
chronic in nature. It is a dose limit based on an 8-hour day/40-hour week
exposure. Like the PEL, it is a lower limit safe dose measurement.
 STEL: (Short Term Exposure Limit) This measure indicates the lower safe
limit for acute exposures. This is the level that may never be exceeded. It is
not an average.
 IDLH: (Immediately Dangerous to Life and Health) This is an atmosphere
(or any other type of risk factor) which presents an immediate or delayed threat
to life, that would cause irreversible adverse health effects, or that would
interfere with an individual's ability to escape unaided from a permit space.

29. Common Hazardous Chemicals In
Confined Space Atmospheres
Nitrogen Carbon
Monoxide
Carbon
Dioxide
Hydrogen Sulfide Methane
Vapor Density 0.97 0.97 1.53 1.19 0.55
LEL 12% 4.3% 5.0%
UEL 75% 46% 15%
PEL (PPM) 50 5000 10 400
IDLH (PPM) 1500 50,000 300
Health Hazards Oxygen
Displacement
Asphyxiant
Headache
Vomiting Loss of
coordination
Oxygen
Displacement
Respiratory failure
Coma Olfactory failure
Headache
Nausea
Irritant

30. Acceptable Entry Conditions
 Oxygen concentration between 19.5% and 23.5%
 Flammable gas concentration less than 10% of LEL
 Airborne dust concentration less than LFL (5 feet)
 Toxic gas Concentration less than PEL

31. Engulfment
 Entrapment by liquid or
finely divided solid
 Hazard made worse if
liquid or solid is moving

32. Other Space Hazards
 Fall threat
 Poor lighting
 Poor temperature control
 Noise
 Clumsiness of protective
equipment