Safety precautions to be observed with cooled premixed gases.

The gas delivered from a cylinder of Entonox (50% nitrous oxide and 50% oxygen) may not contain adequate quantities of oxygen if the cylinder has been cooled and then allowed to warm up in a vertical position.The composition of gas delivered from cylinders cooled to not lower than -40 degrees C. remains unaltered if the cylinders are rewarmed for 24 hours in a horizontal position at a temperature of not less than 5 degrees C.Cylinders of Entonox delivered in cold weather should be stored in a horizontal position at 5 degrees C. or more for at least 24 hours before use.