Confined Spaces – Part 1
An Overview of the
WISHA Confined Spaces Standard
Purpose of This Module
This two-part module provides basic information for employers about the hazards of confined spaces, how to control these hazards and what WISHA requirements apply when employees enter confined spaces.
Some employers may elect to contract out confined space work. In those cases, employers are obligated to fully inform contractors of the confined space hazards at their facilities.
This overview does not replace the confined spaces standard. For the complete WISHA confined space rule requirements, see Confined Spaces - WAC 296-809.
Confined Spaces Overview
Part 1 of this overview will cover the following:
How to identify a confined space,
Confined space hazards,
How to control or eliminate the hazards.
Identifying a Confined Space
What is a confined space?
is large enough to get whole body inside,
is not designed for human occupation,
has limited or restricted entrance or exit.
It must have all three characteristics to be a confined space.
A confined space is an enclosed space that:
Identifying a Confined Space
What is limited or restricted entry or exit?
The ability to easily escape in an emergency is impeded by such obstacles as:
a manhole
a small door or opening
a ladder
a long tunnel
In most cases, a trench is not considered a confined space.
Restricted exit
Exit not restricted
Identifying Confined Spaces
*Examples of confined spaces*
Tanks
Manholes & Sewers
Grain storage bins
Boilers
Other examples include vaults, pipelines, tank cars, and ship holds
Hazards of Confined Spaces
Basic Principles
For a description of an actual confined space fatality, click here.
Confined spaces can be deadly.
Some confined spaces are more hazardous than others.
Confined space conditions can change rapidly from no hazards to life-threatening hazards.
Some confined spaces are so hazardous, a written permit system is required for entry.
The hazards of confined spaces can often be controlled or eliminated before entering.
Hazards of Confined Spaces
What are the main hazards of confined spaces?
Hazard of Confined Spaces
When is a confined space so dangerous a written entry permit system is required?
Hazard Identification
A “hazardous atmosphere” in a confined space has one or more of the following:
Flammable gas, mist or vapor
Oxygen content below 19.5% or above 23.5%
Air contaminant concentrations that would cause death, incapacitation, or permanent health problems
Flammable dusts
You must do air monitoring to determine if a hazardous atmosphere exists.
Hazard Identification
Hazardous Atmospheres – Flammable Gases,
Vapors and Dusts
Flammable gases, vapors or dusts will ignite from a spark or flame if above a level in the air called the “lower flammable limit” (LFL).
Gas or vapor levels higher than 10% of the LFL are considered hazardous and the confined space cannot be entered until levels are reduced.
Amounts above 10% of the LFL are usually toxic as well.
LFL is sometimes called “LEL” – “lower explosive limit”
Hazard Identification
Air
100%
Methane
100%
Air
0%
Methane
0%
Too Rich
5.3%
LFL
15.0%
UFL
Example of flammable gas levels - Methane
Boom!
An open flame or a spark will cause an explosion when methane amount is between 5.3% and 15%, the upper flammable limit (UFL).
Too Lean
Hazard Identification
Hazardous Atmospheres – Oxygen Deficiency
A reduction in oxygen is caused by tank rusting, microbe activity, or replacement by another gas.
Lack of oxygen can cause a person to immediately collapse and die.
Normal air contains 21% oxygen. A space with oxygen content below 19.5 % is considered “oxygen deficient”.
21%
0%
19.5%
Oxygen deficiency exists
Oxygen content
Hazard Identification
*Effects of Oxygen Deficiency*
% Oxygen Symptoms
19.5% - 16% Fatigue, mild impaired coordination
16% - 12% Increased breathing rate and pulse; impaired coordination, perception or judgment
12% - 10% Further increased breathing rate, blue lips, mental confusion
10% - 8% Fainting, nausea, vomiting, mental confusion within few minutes
8% - 6% Collapse, death within 8 minutes
6% - 0% Coma within 40 seconds, death
Using an “inerting gas” like nitrogen, to counteract flammable vapors will result in an oxygen deficiency.
Hazard Identification
A word about oxygen-enriched atmospheres
A confined space with oxygen amount above 23.5% is considered “oxygen-enriched”.
The source of extra oxygen is typically from leaking oxygen cylinders used for oxy-acetylene torches.
Oxygen above 23.5% is a fire or explosion hazard.
Green tanks contain oxygen
Hazard Identification
Hazardous Atmospheres – Toxic Chemicals
Hazard Identification
Hazardous Atmosphere – Toxic Chemicals
The most common toxic chemicals in confined spaces fatalities are hydrogen sulfide and carbon monoxide.
Other toxic chemicals can include welding fumes, vapors from liquid residues in storage tanks, or chemical products used in the confined space.
Chemicals can quickly reach toxic levels in the air of a confined space, especially gases, solvent vapors or sprayed products.
Hazard Identification
Hazardous Atmospheres–Hydrogen Sulfide (H2S)
Hydrogen sulfide gas is commonly found in sewers.
It can be instantly fatal at higher levels in a confined space.
Disturbing sewage sludge can release more hydrogen sulfide gas.
H2S in parts per million (ppm)
30
200
2000
100
1000
Death in minutes
Smell strong odor
Instant collapse
Coughing,red eyes
Loss of smell
600
Unconscious in 30 min.
Hazard Identification
Hazardous Atmospheres – Carbon Monoxide (CO)
Carbon monoxide comes from operating internal combustion engines in or near confined space.
Propane-powered engines also emit carbon monoxide.
Fatal levels of CO are quickly reached in confined spaces.
Propane-powered manlift in a large tank
The PEL for CO is 35 ppm. To see the effects of CO, click here
Hazard Identification
What are the Hazards of Engulfing Material?
Engulfing materials include liquids or loose solids such as grain, sand or other granular material.
People cannot escape when caught in moving loose solids and usually suffocate.
Workers often get engulfed when in-feed or out-feed lines are inadvertently opened or activated.
Hazard Identification
What is Entrapment?
The space is configured in a way that can trap a worker, for example, sides sloping towards the center
Gravel hopper
Sawdust Cyclone
Hazard Identification
Other Recognized Hazards
Electrical lines, steam lines or hydraulic lines
Mechanical hazards (moving parts)
Hazards caused by the work
(welding, painting etc.)
Controlling the Space
The hazards of a confined space can be be controlled in the following ways:
See Part 2 for more information on a written permit system.
Controlling the Space
Warning employees and controlling access
Limit employee access to confined spaces by using entry barriers or locks.
Post warning signs at the entrance of confined spaces.
Make sure that unauthorized workers do not enter the confined space.
Hazard Control
How To Control Hazardous Atmospheres
Drain or pump out liquid contents, if any.
Blank off all in-feeding lines.
Air test and ventilate.
Continue ventilating constantly.
If possible, remove any sludge from outside the confined space.
Exit space if conditions deteriorate.
Hazard Control
Hazardous Atmospheres Dangers
It is difficult to eliminate hazardous atmospheres in most sewers lines.
Tank sludge or sewer sludge can release toxic gases during cleanup.
Toxic or flammable gases can exist in pockets or layers.
Hazard Elimination
How To Eliminate Physical Hazards
Lock-out moving parts
De-energize electrical parts or wiring
Blank or block steam pipes and product in-feeding pipes.
If Hazards Can’t Be Eliminated
If hazards cannot be completely eliminated, there are only two options:
a complete written permit system, or
“alternate procedures.”
Both require training of employees.
See Part 2 for more information on entry procedures.
CWFD Operations
Additional Information
More information is available on WISHA webpage
This presentation is just an overview and does not cover all requirements.
For more information on how to put together a confined space program for your workplace, go to:
For additional assistance, you can call one of our consultants. Click below for local L & I office locations:
http://www.lni.wa.gov/wisha/consultation/regional_consultants.htm