In this tutorial I explain the fundamental principles behind modern anaesthetic vaporizers. I begin by exploring why volatile anaesthetic agents are stored as liquids, why saturated vapour pressure is central to vaporizer design, and the three key problems every vaporizer must solve.

I then compare traditional draw-over vaporizers with modern variable bypass (plenum) vaporizers before examining how contemporary vaporizers achieve accurate and reliable delivery using flow splitting, wicks, baffles and temperature compensation. Finally, I discuss tipping, overfilling and the position of the vaporizer within the circle breathing system.