Pretty sure the Cleveland Clinic had a lot more than 40 negatives though, and a lot more than any personal owner of nitrate films might have. The clinic had been accumulating them in a city of 900,000 for 8 years. Of course fire is fire and any fire can be deadly but the risk of spontaneous combustion, explosion and noxious gases would be much greater with such large quantities.
I'm not sure where ag got the figure of 160 C though. Nitrate film can self-ignite at much lower temps around 100F.
http://www.loc.gov/preservation/care/film.html
wayne, you are right ... there were a boatload of films there, a few 10000x the surface area than a
couple of rolls of / sheets of film ... but still, the fire started with a light bulb on a couple of X-rays.
filament bulbs get HOT. hot enough to burn skin or start a fire.
a few years ago i got a nasty 2nd degree burn from a 60W bulb my arm touched.
while i don't personally have experience with light bulbs causing a fire/burning down my house i am certain
under the right conditions they wouldn't have trouble.
i am sure i am considered an alarmist in these sorts of situations. i'm an alarmist in other situations too
like sticking an 1000W arc lamp in an enlarger head as a light source, or smoking cigarettes while pouring collodion or
eating food in the darkroom, or pulling a "buckley" and dragging a propane tank by the valve instead of the handles.
more than likely enlarging nitrate film won't be troublesome, i'd rather make contact prints and keep the heat/bulb at
a safe distance and then make copy images of the contact prints... but thats just me, kind of paranoid

and to each their own.