What Hazards Should Employees Expect In Confined Spaces?
More than two million Americans are required to enter a permit-required confined space on the job annually. And every year, 100 to 150 of them die from confined space hazards.
Whether a silo, grain bin, trench or cesspool, or large pipe way down in the hole — confined spaces come with similar difficulties and perils and especially the hazard of lacking doors that can hamper both access and well-being.
They’re hard to get in or out, even when not completely enclosed. On a good day, that muddies the communication process; on a bad day it hinders escape or rescue. And because they’re not built for constant human habitation, confined spaces are usually poorly ventilated. That can enable the accumulation of bad air.
If you didn’t already know, a hazardous atmosphere is one of the four main kinds of confined space hazards. In actuality, 4 of the 5 primary types of confined space hazards are due to a hazardous atmosphere.
Here, we consider the 5 most common confined space hazards entries face. We will explain how OSHA defines hazards, how the condition develops and why it can be immediately dangerous to life and health.
Confined Space Hazard - Toxic Atmosphere
OSHA defines a confined space as having a "toxic atmosphere" hazard when it has a toxic substance, at an acutely toxic level, that can kill or injure the employee, cause impairment (incapacitate) to escape unaided or restrict self-rescue from exposure because of harmful health effects.
In other words, a toxic atmosphere is only a hazard if acute symptoms are induced. “The existence of substances that would cause harm over a longer period of time, such as asbestos, doesn’t create a toxic atmosphere — although independent OSHA protections would apply,” she said.
Confined Space Hazard - Oxygen Deficiency
An oxygen deficient atmosphere is defined by OSHA as when the available oxygen in the atmosphere is less than 19.5% volume. Now, for most healthy adults that is not a level where they will notice any ill effects, but below that and — well.
Why is Oxygen Deficiency Hazardous?
Oxygen concentration is found at about 16% of volume, which is when humans begin to experience hypoxia. You might have severe difficulty breathing, nausea or drowsiness. You start to lose consciousness at 12%, brain cells begin dying when levels drop below 6%.
Ultimately, levels of oxygen deprivation can cause asphyxiation and death.
Confined Space Hazard - Oxygen Enrichment
Oxygen makes up 20.9% of Earth's atmosphere by volume in its natural state. Oxygen enriched atmosphere is defined by OSHA as oxygen concentration above 23.5% volume.
Why is Oxygen Enrichment Hazardous?
You may not be aware, but the air you breathe is for the most part inert gas. In fact, over 78% of our atmosphere consists of nitrogen by volume. That renders our pre-industrial atmosphere quite inert to all other chemical species.
And then there's the fact that oxygen is combustible. It speeds up the process of burning, and that’s what makes an oxygen-rich atmosphere so dangerous.
If you have more than 23.5% oxygen collected in one place, say for example a confined space, the clothing on your body becomes fully saturated with oxygen and other flammable materials (like untreated wood) can also saturate with O2 when kept open enough to allow it.
Then, any spark — no matter whether from hot work, a single spark or just static electricity can ignite the oxygen-saturated combustibles and cause them to burn rapidly.
Confined Space Hazard - Flammable or Explosive Atmospheres
Flammable and combustible atmospheres, OSHA reasons for obviously good cause.
Respiratory hazards or an oxygen content of less than 19.5 or more than 23.5 percent by volume, confined space is at atmospheric pressure: Specifically speaking OSHA states that the air in a confined space is considered hazardous if it contains;
- Gas, vapour or mist having a flammable range more than 10% of the lower explosive limit (LFL) or
- A cloud of combustible dust in the air at or above its lower explosive limit
As for the combustible dust, a good rule of thumb is that if it’s thick enough to obscure vision within 5 feet, you should consider there to be a high probability of a flash fire or explosion.
It's worth pointing out that although OSHA uses "LFL," many gas detectors use "LEL" or Lower Explosive Limit. These terms are essentially interchangeable.
Confined Space Hazard - Flowing Liquid or Free Flowing Solids
OSHA considers a confined space to be hazardous if it contains (or may fill with) a material that can engulf an entrant. This includes any flowing liquid or finely divided, flowable solid like dirt or grain.
What Makes Flow Liquids and Dry Powder Dangerous?
The potential dangers of being submerged in a liquid are obvious, but what you don’t know is that any solid small and ‘flowable’ enough can be just as hazardous.
When you're dealing with liquids and free-flowing solids, one danger is englufment of an entrant. While the strangling and constricting capabilities of materials may be a risk in and of themselves because they can apply force to the body capable of resulting in death through strangulation, constriction or crushing.
Engulfment can also indicate that the entrant is “physically captured” in a confined space, where he or she may be exposed to other types of hazards — for example, if the space were flooded or contained a toxic atmosphere. Those who are swallowed by flowing solids, however, can be particularly challenging to rescue because of the weight of the material on top of them.
Finally, aspiration from liquid flow or loose solids is yet another hazard. A liquid or a finely divided solid particle can be drawn into the lung, flooding or blocking the respiratory system with resulting asphyxiation and death. Even without engulfment, powders can be a risk for asphyxiation if they go airborne and clog the airways, he added.
Meet Confined Space Training Requirements
To make certain that workers who enter confined spaces fully know the hazards involved and how to mitigate them, OSHA mandates a training class for all entrants in confined space hazards.