IDLH threshold is greater than what ppm?

• A. 1000 ppm
• B. 5000 ppm
• C. 20000 ppm
• D. 10000 ppm

Answer: (D)

IDLH means Immediately Dangerous to Life or Health, and it marks the concentration at which exposure would pose an immediate threat to life or health or impede escape. The standard benchmark for this threshold is 10,000 ppm, which equals 1% by volume in air. When the contaminant concentration reaches or exceeds this level, conditions are considered immediately dangerous and require protective gear such as a supplied-air respirator or SCBA and rapid evacuation. So the threshold in question is 10,000 ppm. Lower values like 1,000 or 5,000 ppm wouldn’t generally be treated as IDLH for most substances, while higher numbers like 20,000 ppm exceed the typical IDLH reference point.