To think it's a fire risk to leave the phone charger turned on?

[iveburntthetoast]

After DH has charged his phone and disconnects it, he always leaves the plug turned on at the wall. AIBU in thinking he should turn it off when not in use as it's a fire risk?

Never turned off, not a fire risk, no current is drawn when nothing is plugged into it.

Computers:
Many (desktops) have a 'sleep' mode where you switch it on by a small push switch on the front. This leaves a very small circuit still connected to the mains and POTENTIALLY that could fail and burn. Most computers will have a 'real' mains switch (often at the back next to the mains inlet) which would turn it off completely, thus safer.
Printers often do not have a 'real' power switch so for safety should be turned off at the mains socket. A 'power socket strip' with a switch might be convenient way to shut off all the gear.
Laptops are a tricky one as you can obviously unplug the charger, and should do, but like mobile phones the computer itself is never REALLY off, just a deep sleep! Since the issue with mobiles spontaneously combusting in the last year or so, it would be sensible to place your laptop on a non flammable surface away from paper etc when not in use.

Because like all appliances it's potentially a fire risk.

Personally I leave mine plugged in, in case you wondered. Along with some other stuff that it's too much hassle to unplug.

My friend works in the care industry and they get regular fire safety checks. Apparently plug in air fresheners are a massive risk for fire. I suppose it does made sense after all you are plugging strong chemicals into the wall to heat up.

Only if the plug thinks it's a Samsung.