The metal content of e-cigarette vapour has been analysed; even for relatively crude first-generation devices, the metal content is well within established safe exposure limits.

Stainless steel coils facilitate temperature-controlled vaporisation, which is a crucial advance in harm reduction. Controlling the temperature of vaporisation significantly reduces the production of aldehydes and aromatic hydrocarbons, which are created by the thermal decomposition of propylene glycol and glycerine; these decomposition products are by far the most dangerous components of e-cigarette vapour.

http://www.ecigarette-research.org/research/index.php/resear... http://onlinelibrary.wiley.com/doi/10.1111/add.12942/abstrac...

do you know anything about the wire temperature in these things? I looked at both links and didn't see any numbers outside the paywall. Another comment mentions a vapor temperature of <260C, but nothing about the wire temperatures.

Stainless or Kanthal at 500C or something should indeed be quite inert, it's just not that hot.

200C to 260C is the normal temperature range, measured at the coil. Temperature-controlled devices use the coil itself as the temperature sensor by continuously measuring the resistance of the coil. The device calibrates each coil at room temperature when it is first installed. Stainless steel has a sufficiently high temperature coefficient of resistance to measure temperature quite accurately. Kanthal doesn't work with this method, because by design it has a very low temperature coefficient of resistance.

Power-controlled devices rarely exceed 300C in normal use, because there is considerable airflow over the coil combined with evaporative cooling. Excessive temperatures can be reached if the device is inadvertently activated, or if the liquid flow to the coil is inadequate.

As you say, kanthal and stainless steel should be very stable at these temperatures. Pure titanium wire also works with temperature control and completely avoids the issue of chromium, but there is some debate over the potential risks of titanium dioxide nanoparticles.