Which reaction can run away? Cellulose -> NC?

Not really, but setting up the nitration mix is always a somewhat risky endeavour if you're heating it.

Nox aint got no friends ...

Basically, because the nitration process generates heat, the solution gets hotter, and if it gets too hot it will start spewing NOx fumes. White fumes at first, and if it runs away, scary red/brown ones. Never had one run away myself, although it fumes white if I don't cool it/mix in things slowly. My chem is a bit rusty but it has something to do with HNO3 breaking down. FYI this applies to all nitrations; that's why you do them COOOOOOLD

You could apply that rule to every procedure that generates heat when it's not absolutely mandatory.

Heat = BAD.

Yes its the nitrocellulose reaction that can have a runaway. For those of you that don't know what a runaway is first don't try NC because you don't know enough and secondly know its not a fun thing. First off like stated it will start fuming brown/red fumes then it will will start making more fumes and it will start to "boil" Which means you know how when you boil water you get the bubbles and sometimes the water spills out or the bubbles pop and some water goes everywhere? Well imagine this with a mixture of HNO3/H2SO4. And of course lots of heat is generated so not only is the acid nice and acidy but its also hot. Luckily when I had this happen it was in a fume hood and I had a bucket of ice not to far so it wasn't to hard to keep it under controlled conditions and get the runaway to stop. But trust me it definatly leaves a big fucking pain in the ass mess, and if it had been in anything but that fume hood might have done some damage.

So the one step you do not want to forget is the ice bath. Seriously the extra miniute and ice is worth it.

Any nitration can cause a runaway if it isn't kept cool. you know it is running away when it starts spewing out brownish red gas and starts bubbling.

No, you know it's GOING to go haywire when it starts to fizzle and make little bubbles, meaning it's beginning to pump Nox and that you will soon have to bail out if you don't cool it ASAP.

Seriously if you wait for a cloud a brown fumes to start generating before you go "uh ? something might be wrong", you shouldn't even touch HNO3. Anyways if you go for that "method" of spotting a runaway nitration you won't survive long enough to testify about it.

A few times *might* be ok with good ventilation, but over time you'll end up frying your organs, so...

I never said to wait until the gases are bubbling out did I? No i dont think i did. I said you know you have a runaway when it is bubbling out gases. You want to cool it and stop it *before* it runs away. So a runaway is not when it just starts to bubble or disperse NOx. when it just starts means it is starting to run away not currently running away.