The effects of the paraffin hydrocarbons vary with the volatility. The gaseous hydrocarbons, such as methane, ethane, etc., have but slight anesthetic effects and are hazardous only when present in sufficient concentration to dilute the oxygen to a point below that necessary to sustain life. With the volatile liquid hydrocarbons, or with the next-higher fraction, the anesthetic action predominates, and with the higher molecular weights or with the less volatile compounds, the anesthetic increases, but at the same time an irritant action becomes more pronounced. For information concerning toxic and hazardous properties of these materials, see the individual compounds. Paraffins are common air contaminants. Can be a dangerous fire hazard depending on volatility.