7.1 OSHA Safety: Confined Spaces

7.1 OSHA Safety: Confined Spaces (OSHA 1910.146)

Safety is the absolute most critical aspect of a Water Distribution Operator's job, and confined spaces represent one of the most hazardous environments an operator will encounter. OSHA 1910.146 is the primary standard that governs the procedures and requirements for safely entering and working in confined spaces. Understanding this standard, the hazards involved, and the proper safety procedures is essential not only for passing the certification exam but for ensuring the survival of the operator and their crew.

Defining a Confined Space

A confined space is defined by three specific criteria. A space must meet all three of these criteria to be classified as a confined space:

1. Large enough and so configured that an employee can bodily enter and perform assigned work. If you cannot get into the space, it is not a confined space.
2. Has limited or restricted means for entry or exit. Examples include tanks, vessels, silos, storage bins, hoppers, vaults, and pits. They often require ladders or hoists to enter and exit.
3. Is not designed for continuous employee occupancy. These spaces are designed for storing water, housing equipment, or other operational purposes, not for humans to work in on a regular, ongoing basis.

Permit-Required Confined Spaces

Not all confined spaces require a permit for entry. A permit-required confined space (often simply called a "permit space") is a confined space that has one or more of the following additional characteristics:

• Contains or has a potential to contain a hazardous atmosphere.
• Contains a material that has the potential for engulfing an entrant (like water, mud, or sand).
• Has an internal configuration such that an entrant could be trapped or asphyxiated by inwardly converging walls or by a floor which slopes downward and tapers to a smaller cross-section.
• Contains any other recognized serious safety or health hazard (such as exposed live electrical wires or unguarded mechanical moving parts).

If a space meets any of these criteria, a formal, written Permit Space Program must be established and utilized before any entry can occur.

Atmospheric Hazards

Atmospheric hazards are the leading cause of death in confined spaces. Because confined spaces have limited ventilation, gases and vapors can accumulate to dangerous levels.

Oxygen Levels

The most basic atmospheric requirement is a safe level of oxygen. OSHA regulations specify confined space oxygen level limits (19.5% to 23.5%). The normal atmosphere is composed of approximately 20.9% oxygen.

• Oxygen Deficient: Less than 19.5% oxygen. At these levels, physical and mental coordination is impaired.
• Oxygen Enriched: Greater than 23.5% oxygen. This is a severe fire hazard. Materials that normally burn slowly will burn rapidly and violently in an oxygen-enriched environment.

Flammable and Explosive Atmospheres

Combustible gases and vapors must be measured. The Lower Explosive Limit (LEL), also known as the Lower Flammable Limit (LFL), is the lowest concentration of a gas or vapor that will ignite if a source of ignition is present.

• Entry is generally prohibited if the LEL is greater than 10%.

Toxic Gases

Two of the most common and deadly toxic gases found in water distribution systems are Hydrogen Sulfide (H2S) and Carbon Monoxide (CO).

Hydrogen Sulfide (H2S):

• Characteristics: Colorless gas with a distinct "rotten egg" smell at very low concentrations.
• Danger: It is heavier than air and settles in low-lying areas (like the bottom of a vault or trench). It rapidly deadens the sense of smell (olfactory fatigue), meaning you may no longer smell it even as concentrations reach lethal levels.
• Effects: It is highly toxic and can cause instant unconsciousness and death at high concentrations.

Carbon Monoxide (CO):

• Characteristics: Colorless, odorless, and tasteless gas.
• Danger: Produced by incomplete combustion (e.g., gasoline engines, generators, pumps). It has an affinity for hemoglobin that is over 200 times greater than oxygen, meaning it quickly displaces oxygen in the blood.
• Effects: Causes headaches, dizziness, nausea, and eventually unconsciousness and death due to chemical asphyxiation.

Atmospheric Testing Order

When testing a confined space, testing must be performed in a specific, strict order. This is because some sensors require oxygen to function properly, and an explosive atmosphere is an immediate physical threat.

1. Oxygen: Always test first. If oxygen levels are too low, the combustible gas meter may give a false reading.
2. Flammability (LEL): Test for explosive gases and vapors next. An explosion is an immediate physical hazard.
3. Toxicity: Finally, test for toxic gases like H2S and CO.

Testing must evaluate all levels of the space (top, middle, and bottom) because gases have different weights relative to air. For example, H2S is heavier and sinks, while methane is lighter and rises.

The Entry Team: Roles and Responsibilities

A successful and safe confined space entry requires a coordinated team with distinct roles.

The Entrant

The authorized entrant is the person who physically goes into the confined space. Their responsibilities include:

• Knowing the hazards that may be faced during entry.
• Using equipment properly.
• Communicating with the attendant as necessary.
• Alerting the attendant whenever any warning sign or symptom of exposure to a dangerous situation, or a prohibited condition, is recognized.
• Exiting the space as quickly as possible whenever an order to evacuate is given.

The Attendant

The attendant, often called the "hole watch," remains outside the confined space at all times during the entry. This is a critical life-safety role.

• Crucial Rule: The attendant must never enter the space to attempt a rescue, no matter what happens to the entrant. Over 50% of confined space fatalities are would-be rescuers who enter without proper precautions.
• Responsibilities include maintaining an accurate count of entrants, communicating with entrants, monitoring activities inside and outside the space, and ordering an evacuation if conditions become unsafe. The attendant must perform non-entry rescues using lifelines and mechanical advantage systems if necessary. Unlike trench work where OSHA requires ladders every 25 ft of travel, confined space entry relies on direct retrieval lines whenever possible.

The Entry Supervisor

The entry supervisor is responsible for overseeing the entire operation.

• They must verify that all required tests have been conducted and all procedures and equipment specified by the permit are in place before endorsing the permit and allowing entry to begin.
• They have the authority to terminate the entry and cancel the permit if acceptable entry conditions are not maintained.
• They must ensure that rescue services are available and that the means for summoning them are operable.

By strictly adhering to OSHA 1910.146 and understanding these fundamental principles, Water Distribution Operators can safely navigate the hazards associated with confined spaces.