It seems that a few Apple warranties have been deemed void due to the fact that the owner was a a smoker, and consequently their Macs were contaminated. The Applecare contract says nothing about this, and the list of toxic materials includes other such dangerous household items as talcum powder and isopropyl alcohol. There’s a long discussion of consumer rights and nanny laws and all that sort of thing just waiting to be pulled out of this story, but let’s not and say we did.
I’m really more interested in whether any of these ostensibly dangerous materials actually do have an effect on your computer’s hardware. In my experience, the most lethal thing in the house is just the dust and fluff that gets sucked into your fan intakes. That or coffee.