Immediately Dangerous to Life & Health (IDLH).

A work environment that poses an immediate threat to an employee’s life and health are called Immediately Dangerous to Life & Health (IDLH).

An IDLH condition is one that poses an immediate or delayed threat to life or that would cause irreversible adverse health effects or that would interfere with an individual's ability to escape unaided from a space.

NOTE: Some materials may produce immediate transient effects that, even if severe, may pass without medical attention, but are followed by sudden, possibly fatal collapse 12-72 hours after exposure. The victim "feels normal" from recovery from transient effects until collapse. Such materials in hazardous quantities are considered to be "immediately" dangerous to life or health.

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Potential IDLH Environments in Construction

Because of their potential to contain hazardous atmospheres, confined or enclosed spaces are suspect IDLH environments.

Confined & Enclosed Spaces:

• Storage Tanks
• Process Vessels
• Bins
• Boilers
• Ventilation or Exhaust Ducts
• Sewers & Manholes
• Underground Utility Vaults
• Tunnels
• Pipelines
• Open top spaces more than 4 feet in depth
• Temporary Enclosures (heating enclosures for break)
• Dumpsters
• Stair-wells
• Elevator Shafts

• Basements
• Attics
• Trenches & Excavations
  
• Hazardous atmospheres may exist in trenches. When a trench reaches a depth of 4 feet, they must be evaluated for IDLH conditions by a competent person.
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