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Confined Space Safety in Construction.

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Presentation on theme: "Confined Space Safety in Construction."— Presentation transcript:

1 Confined Space Safety in Construction

2 (b)(6)(i) All employees required to enter into confined or enclosed spaces shall be instructed as to the nature of the hazards involved, the necessary precautions to be taken, and in the use of protective and emergency equipment required. The employer shall comply with any specific regulations that apply to work in dangerous or potentially dangerous areas.

3 (b)(6)(ii) ”Confined or enclosed space" means any space having a limited means of egress, which is subject to the accumulation of toxic or flammable contaminants or has an oxygen deficient atmosphere.

4 (b)(6)(ii) Confined or enclosed spaces include, but are not limited to, storage tanks, process vessels, bins, boilers, ventilation or exhaust ducts, sewers, underground utility vaults, tunnels, pipelines, and open top spaces more than 4 feet in depth such as pits, tubs, vaults, and vessels.

5 1926.353(b) Welding, cutting, and heating in confined spaces.
Either general mechanical or local exhaust ventilation meeting the requirements of paragraph (a) of this section shall be provided whenever welding, cutting, or heating is performed in a confined space.

6 1926.353(b) Welding, cutting, and heating in confined spaces.
When sufficient ventilation cannot be obtained without blocking the means of access, employees in the confined space shall be protected by air line respirators. An employee on the outside of such a confined space assigned to maintain communication with those working within it and to aid them in an emergency.

7 1926.353(b) Welding, cutting, and heating in confined spaces.
"Lifelines." Where a welder must enter a confined space through a manhole or other small opening, means shall be provided for quickly removing him in case of emergency.

8 1926.353(b) Welding, cutting, and heating in confined spaces.
When safety belts and lifelines are used for this purpose they shall be so attached to the welder's body that his body cannot be jammed in a small exit opening. An attendant with a pre-planned rescue procedure shall be stationed outside to observe the welder at all times and be capable of putting rescue operations into effect.

9 (g)(1) Where oxygen deficiency (atmospheres containing less than 19.5 percent oxygen) or a hazardous atmosphere exists or could reasonably be expected to exist, such as in excavations in landfill areas or excavations in areas where hazardous substances are stored nearby, the atmospheres in the excavation shall be tested before employees enter excavations greater than 4 feet (1.22 m) in depth.

10 Background Many workplaces contain spaces which are "confined”.
Their configurations hinder the activities of any employees who enter, work in, and exit them. Employees who work in process vessels must squeeze in and out through narrow openings or perform their tasks while cramped or contorted. Septic Tanks Sewage Digester Pumping/Lifting Stations Silo’s Vats Ducts Utility Vaults Boilers & Pipeling

11 OSHA Perspective In some cases, confinement itself poses entrapment hazards. In other cases, confined space work keeps employees closer to hazards, such as asphyxiating atmospheres or the moving parts of machinery. Workers often introduce hazards through materials they bring into the confined space, and the tasks they perform: Painting Solvent cleaning Welding

12 NIOSH Definition Any space which, by design, has:
limited openings for entry and exit; unfavorable natural ventilation which could contain or produce dangerous air contaminants, and; which is not intended for continuous employee occupancy.

13 Statistics NIOSH report: 1993 - 1996 276 Confined Space incidents
Resulted in 234 deaths 193 injuries Up to half of those killed in confined spaces were rescuers

14 Overview Failure to recognize confined space hazards is high on the list of accident causes

15 Overview First Priority - Define the hazards of the space:
Restricted areas within the confined space Voids The nature of the contaminants present The size of the space The type of work to be performed The number of people involved

16 Ventilation Considerations
The ventilation air should not create an additional hazard: Recirculation of contaminants Improper arrangement of the inlet duct The substitution of anything other than fresh (normal) air (approximately 20.9% oxygen, % nitrogen, and 1% argon with small amounts of various other gases).

17 Categories of Confined Spaces
1. Open tops and with a depth that will restrict the natural movement of air 2. Enclosed spaces with very limited openings for entry.

18 Properties of Gasses - Open Top Confined Spaces
Gases that are heavier than air (butane, propane, and other hydrocarbons) remain in depressions and will flow to low points where they are difficult to remove Water tanks that appear harmless may develop toxic atmospheres such as hydrogen sulfide from the vaporization of contaminated water

19 Properties of Gasses - Closed Vessel Confined Spaces
Gases which are heavier than air such as carbon dioxide and propane, may lie in a tank or vault for hours or even days after the containers have been opened.

20 Properties of Gasses - Closed Vessel Confined Spaces
Because some gases are odorless, the hazard may be overlooked with fatal results. Gases that are lighter then air may also be trapped within an enclosed type confined space, especially those with access from the bottom or side.

21 Confined Space Hazards - Controlling Factors
(1) The material stored or used in the confined space; (2) The activity carried out, (3) The external environment,

22 Combination Hazards The most hazardous kind of confined space is the type that combines limited access and mechanical devices. Boilers usually contain power-driven equipment which, unless properly isolated, may be inadvertently activated after entry.

23 Hazardous Atmospheres

24 Flammable Atmospheres
Enriched oxygen atmospheres, Vaporization of flammable liquids, Byproducts of work, Chemical reactions, Concentrations of combustible dusts

25 Flammable Atmospheres
The byproducts of work procedures can generate flammable or explosive conditions within a confined space.

26 Carbon Monoxide Fatal at 1000 ppm in air Dangerous at 200 ppm

27 Carbon Dioxide (CO2) Colorless, odorless noncombustible gas
Heavier than air Common in solid and compressed liquid forms Carbonation Inerting Organic decay (grain elevators, sewers, storage bins, wells) Fermentation (digestors, molasses pits, beer and wine vats)

28 CO2 (cont’d) PEL = 5,000 ppm - TWA (Table Z-1)
TLV/REL = 5,000 ppm - TWA; 30,000 ppm - STEL IDLH = 50,000 ppm LEL = none

29 Carbon Monoxide (CO) Colorless, odorless gas Slightly lighter than air
Chemical asphyxiant Primary source: incomplete combustion of organic material Gasoline-fueled combustion engines

30 CO (cont’d) PEL = 35 ppm - TWA TLV = 25 ppm - TWA
BEI: <3.5% COHb; 20 ppm (end-exhaled air) REL = 200 ppm - STEL; 35 ppm - TWA IDLH = 1500 ppm LEL = 12.5%; UEL = 74.2%

31 Concentration of CO Necessary to Produce Symptoms
Percent ppm Effects Possibly headache, mild frontal in 2-3 hrs. Headache, frontal, and nausea after 1-2 hrs.; occipital after 2-1/2 to 3-1/2 hrs. Headache, dizziness and nausea in 3/4 hour, collapse and possibly unconsciousness in 2 hrs. 0.16 1,600 Headache, dizziness and nausea in 20 min.; collapse, unconsciousness, possibly death in 2 hr. 0.32 3,200 Headache and dizziness in 5 to 10 min., unconsciousness and danger of death in 30 min. 0.64 6,400 Headache and dizziness in 1 to2 min., unconsciousness and danger of death in 10 to 15 min. ,800 Immediate effect; unconsciousness and danger of death in 1 to 3 min. (Source: Hamilton & Hardy)

32 Symptoms of CO Exposure
Percent* Symptoms 0-10 Shortness of breath on exertion Tightness across forehead, slight headache Throbbing headache Severe headache, nausea, vomiting, collapse on exertion All symptoms increased, pulse rate and breathing increased Coma, interrupted breathing (Cheyne-Stokes), death * Percent saturation of Hemoglobin with CO [Blood Levels] (Adapted from Dubois and Geiling)

33 Carbon Monoxide Any untested atmosphere must be suspect
Carbon monoxide must be tested for specifically.

34 Oxygen Displacement Helium Argon Nitrogen Argon

35 Oxygen Deprivation 21% 17% % 6 -10% 6%

36 Oxygen-Deficient Atmospheres
O2 Content 15-19% Effects and Symptoms (at patm) Decreased ability to work strenuously. May impair coordination and induce early symptoms in persons with coronory, pulmonary, or circulatory problems. Respiration increases in exertion, pulse up, impaired coordination, perception, and judgment. Respiration further increases in rate and depth, poor judgment, lips blue. Mental failure, fainting, unconsciousness, ashen face, blueness of lips, nausea, and vomiting. 8 min., 100% fatal; 6 min., 50% fatal; 4-5 min., recovery with treatment. Coma in 40 sec., convulsions, respiration ceases, death. 12-14% 10-12% 8-10% 6-8% 4-6% NOTE: Exposure to atmospheres containing 12% or less oxygen will bring about unconsciousness without warning and so quickly that individuals cannot help or protect themselves. (Source: Compressed Gas Association Bulletin SB-2)


38 Physical Hazards

39 Physical Hazards Thermal effects (heat and cold), Noise Vibration
Radiation Fatigue while working in a confined space

40 Thermal Hazards (1) Air temperature, (2) Air velocity,
(3) Moisture contained in the air, and (4) Radiant heat.

41 Noise Reverberation Communication Commands

42 Vibration Whole body Segmental Tools

43 Definition-NIOSH Any space which, by design, has limited openings for entry and exit; unfavorable natural ventilation which could contain or produce dangerous air contaminants, and which is not intended for continuous employee occupancy. Roll-off box example closed door vs non-closed



46 Hazardous atmosphere Flammable gas, vapor, or mist in excess of 10 percent of its lower flammable limit (LFL) Airborne combustible dust at a concentration that meets or exceeds its LFL; NOTE: This concentration may be approximated as a condition in which the dust obscures vision at a distance of 5 feet (1.52 m) or less.

47 Hazardous atmosphere Atmospheric oxygen concentration below 19.5 percent or above 23.5 percent; Atmospheric concentration of any substance for which a dose or a permissible exposure limit is published Any other atmospheric condition that is immediately dangerous to life or health.

48 Inerting The displacement of the atmosphere in a permit space by a noncombustible gas (such as nitrogen) to such an extent that the resulting atmosphere is noncombustible. NOTE: This procedure produces an IDLH oxygen-deficient atmosphere.

49 Retrieval system The equipment (including a retrieval line, chest or full-body harness, wristlets, if appropriate, and a lifting device or anchor) used for non-entry rescue of persons from permit spaces.

50 Communication Summoning Help Body Positions Voice Alarms

51 Self Rescue Usually initiated by worker Worker removes self
No rescuer entry required Entrant must know reasons for self rescue

52 Entry Rescue Most difficult and risky
Requires training, equipment and coordination of efforts

53 Respirators for IDLH Atmospheres
Combination Full Facepiece Pressure Demand SAR with Auxiliary Self-Contained Air Supply Full Facepiece Pressure Demand SCBA

54 Lanyard

55 Bosun Chair



58 Davit Arm

59 Vehicle-Mounted Davit

60 Confined space testing
FOUR-GAS DETECTOR Oxygen content Flammability / explosion potential Carbon monoxide Hydrogen sulfide Critical issues - Training Procedures Calibration

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