The theory is that 110 volts, with a "centre tap earth" has only 55 volts to earth. The theory is also that it takes 60 volts to kill you. Now I haven't tried these theories, but there you are.
Many people use 110 volt equipment and plug it into a 240 volt / 110 volt transformer. Now the transformer is just as dangerous as a 240 volt tool. Many of these transformers are left in puddles, cases cracked, leads damaged, etc etc.
Any area where water can be present is limited to 24 volts.
To be honest, in this day and age, you could get any hand tool as a cordless, and save a whole lot of hassle.
You will see equipmenty over 110 volts on many building sites. A large concrete mixer could well be 3-phase 415 volts.
It is HAND HELD EQUIPMENT that is limited to 110 volts.
So if your carpet cleaner is a "tube and wand" like a Prochem Steempro, 240 volts is fine. If it's a "walk behind", like a Rug Doctor, you might need 110 volts. If you are using a Pressure Washer, you aren't holding the equipment (only the lance, which like a CC wand is isolated by a long hose) so 240 should be ok. If you are using an electric drill, then you need 110. (but just get a good cordless)
EXCEPT: the 110 volt rule is for whilst construction is taking place. Now I don't think many people lay carpets before construction is completed, so carpet cleaners working on new estates are fine with 240 volts (as the house you are in is not under construction)
Oh..... I almost forgot..... thanks to Europe, our 240 volts is now called 230 volts.