The word 'infrared' gets tossed around quite a bit, but literally means beyond red or the wavelengths of light that are longer than red or greater than about 700 nm (less for 'red color blindness'). Usually, the military is interested in the middle wave infrared (MWIR) and the long wave infrared (LWIR) as these bands don't require illumination. The near infrared is what would be handy in the darkroom, from 700nm to about 1100nm is the most common of the near infrared. This is a very economically band to see, because all consumer electronic imagers (digital cameras, videocams,etc.) are capable of seeing in this band because they use silicon sensors. They actually see better in the near IR than in the visible. However, to make everything look right in your pictures, the manufacturer places an IR cutoff filter over the detector that stops all the 700 nm and beyond light from hitting the detector. If this can be removed (it looks like a light blue filter), any of the electronic cameras can see IR. Of course there is a focus shift in the lens and to see in the dark, you would need an IR source which would either be a tungsten source with a good IR pass filter or an IR light emitting diode. The IR LED is probably cheaper, but I don't know.
I think there are a few cameras out there that don't have the IR cutoff filter in them. They would be BW surveillance cameras. There is one in most ATM behind that black square. The lack of this filter would give increased sensitivity. There was some talk about these cameras a few years back and their ability to see through some fabrics.