Light Hydrocarbon Gases: A Narcotic, Asphyxiant, or Flammable Hazard?

Abstract

A model used to predict the potency of anesthetic gases is proposed as being applicable to predicting the onset of narcosis from exposure to light hydrocarbon gases (C1 to C3) in a workplace setting. The validity of the model is confirmed using human experience from diving (nitrogen narcosis) and workplace exposure to toluene.

The solubility of a gas or vapor in olive oil must be known to use this predictive model. The air/olive oil partition coefficients of 15 hydrocarbons (C1 to C4, plus hexane and benzene) have been measured and are reported, many for the first time (methane 0.89; ethane 2.1; propane 5.9; and butane 17.1).

The model predicts that the light hydrocarbon gases are not just simple asphyxiants but fast-acting agents inducing narcosis as expressed in loss of judgment, disorientation, dizziness, and light headedness.

The recommendation is made that in addition to an 8-hour time-weighted average exposure limit (1000 ppm, set on a basis of good industrial hygiene practice), a maximum exposure limit is needed. This is set at 10 percent of the lower explosive limit (LEL) on the basis of avoidance of narcosis and recognition of the explosive hazards of the gases. The implications of such a limit in the workplace are discussed. In particular, oil and gas workers who are responding to a combustible gas alarm (set at 10% of the LEL) need to use supplied-air respiratory protection before entering the building where the alarm has tripped. Drummond, I.: Light Hydrocarbon Gases: A Narcotic, Asphyxiant, or Flammable Hazard? Appl. Occup. Environ. Hyg. 8(2):120-125; 1993.