Gases - Dangerous Concentration Levels

Dangerous vs. tolerable concentration levels for some industrial gases.

GasTolerable > 1 hour (o/oo)Tolerable < 1 hour (o/oo)Immediately Dangerous (o/oo)
Ammonia0.10.33.5
Bromine Vapor0.0010.0040.05
Carbon Dioxide103040
Carbon Monoxide0.20.52
Chlorine Vapor0.0010.0040.05
Hydrochloric Acid0.010.051.5
Hydrogen Sulphide0.20.6
Iodine Vapor0.00050.0030.05
Sulphuric Acid0.050.5

Unit Conversion:

  • 1 ppm = 10⁻⁶ = 0.0001 o/o = 0.001 o/oo
  • 1 o/oo = 1000 ppm

Abbreviations:

  • o/oo = parts per thousand
  • ppm = parts per million