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.

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.

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

Oxygen Deficient Atmospheres Purging Natural processes Gas displacement Oxygen absorption

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

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.

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.

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.

Vapor Density Vapor Densities of Selected Gases and Vapors: Methane0.55 Carbon Monoxide0.96 Hydrogen Sulfide1.19 Freon (R-12)4.30

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.

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

Flammable Gases – The Fire Triangle

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.

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.

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

FLAMMABLE RANGE Flammable Range of Selected Gases and Vapors Flammable Vapor or Gas LELUEL  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%

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

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

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

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.

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

Chemical reactions from:  Manufacturing process  Products Stored  Drying Paints  Oxidation / reduction reactions  Cleaning with acids or solvents u Rusting of metal u Curing of concrete u Rotting / decomposing / fermentation

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

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

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

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.

Common Hazardous Chemicals In Confined Space Atmospheres NitrogenCarbon Monoxide Carbon Dioxide Hydrogen SulfideMethane Vapor Density LEL12%4.3%5.0% UEL75%46%15% PEL (PPM) IDLH (PPM)150050, Health HazardsOxygen Displacement Asphyxiant Headache Vomiting Loss of coordination Oxygen Displacement Respiratory failure Coma Olfactory failure Headache Nausea Irritant

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

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

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