Should I worry about a fire?

By doing what you suggest, then maybe individual outlets and the wires that run to them may not get too hot, but the circuit itself is still drawing more than it is rated for, it sounds like. Therefore, it will get hot at the breaker and the primary wire running from it, likely tripping the breaker (or worse).
I am not an electrician. I do most of my own work though.

Make sure:

The fan and adapter have the same current output (ac or dc). DC fans need a DC output adapter.

DO NOT ACCEED the voltage on the fan when selecting a power adapter. 12v fan/12v or less adapter. Don't go to far below or you'll start losing power.

Do not select an adapter with LESS amperage than the fan. But don't go to far above either. For most pc fans you shouldn't need to go above 1 amp. Example of amps: 550 mA or miliamps = .55 amps

Hope this helps.

I don't under stAnd the plug In I have says out put and input which one do I loook for?

Panda Bear said:

So I have been tripping out about my pc grow box starting a fire!! Ha well the things that worry me the most is that the fans will spark something because I turned up the fans and it gets really hit the part that pluggs into the wall. Big fans are 12v and the other is a fan that is 12 volts too and the plug in is 18 v but this one is a bigger one.
Any opinions???

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You should not worry about a fire..I doubt your drawing more then ten amps from that outlet... but if your worried, check what other appliances are being used with that circuit and disconnect if you please, but most modern household elecronics, not including kichen appliances, (which all should have dedicated circuits) draw very little amperage...

Panda Bear said:

I don't under stAnd the plug In I have says out put and input which one do I loook for?

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Output. You're adapter should say something like "Input 110volts ac / Output 12volts dc". Make sure the output type matches your fan. You don't want the output voltage on the adapter to be greater than the voltage of your fan.

What would happen tothe fan? Becaus I got a big fan and it says 12volts and I'm using a 15 watt amps adapter for it.