A guide for monitoring atmospheric hazards in confined spaces. Confined spaces expose entrants to a variety of atmospheric hazards. These include: Acute Illness, Death, Entrapment, Severe Injury
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What is a confined space?
A confined space, according to OSHA, is any space which:
- Is large enough for a person to enter, and perform work.
- Is not designed for permanent human occupancy.
- Has limited or restricted means for entry and/or exit.
Examples of confined spaces include:
Agriculture Silos | Grain Elevators | Fuel Tanks | Storage Tanks | Tunnels | Underground Vaults
* Entry into confined spaces is part of the daily routine for most workers with industrial jobs.
Types of Atmospheric Hazards
- Atmospheric oxygen concentration:
- Oxygen deficiency – below 19.5%
- Oxygen enrichment – above 23.5%
- Combustible gases
- Toxic gases
The air inside a confined space must be tested before employees are allowed to enter.
* Atmospheric testing to evaluate whether or not acceptable conditions for entry exist within a confined space, and for the evaluation of any hazards present.
The recommended order for testing confined spaces for atmospheric hazards is:
Oxygen: Proper oxygen levels must be present.
Combustible Gases: No combustible gases must be present.
Toxic Gases: Any toxic gases present inside the confined space – commonly carbon monoxide [CO] and hydrogen sulfide [H2S] – should be below OSHA permissible exposure limits.
* Samples should be taken at the top, middle, and bottom of a confined space to properly check for varying concentrations of different gases and vapors.
- Confined spaces should be tested routinely to ensure that atmospheric conditions remain safe for entry.
- All testing should be conducted using equipment specifically designed to detect chemicals, gases, and vapors which may be present at levels below defined exposure limits.