With shredder use on the rise at home and in small offices because of the desire to prevent identity theft and limit liability, some characteristics of shredders are turning out to be serious safety risks to small children and pets, and to a lesser extent to careless adults. Curious animals and children poke into the feed throats where they see the paper disappearing, with horrible and sometimes fatal results. It doesn't take much imagination to see what a cross-cut shredder could do to little fingers or to animal tongues — in fact it's best not to think about it since the results can be too awful to contemplate. A dog lost the first two inches of its tongue — a kitten had its face destroyed and had to be put down — one child lost the last joints on three fingers - another had four fingers reduced to stumps.
All this is because of the way the shredders operate. All of them - cross- or ribbon-cut — PULL the paper down into their throats. All of them are built on the assumption that only material meant to be shredded will get into the throats, so while most have a reverser to help in clearing jams, few if any have a pressure release that will open the mechanism if to large an object gets into the path. (Old-fashioned mangles — for squeezing the water out of just-washed clothes — had a mechanism that would release the rollers if something too big tried to go through. This is the sort of thing that's needed.) Shredders operate so fast that there's almost no time to react if one's fingers are in danger. So dogs will sniff and their lolling tongues will get caught — cats will sniff and poke their paws in — and kids will stick their hands in, all unaware of what's going to happen.
Until safety standards catch up with this issue, the only thing that can be done is to keep the pets and the kids strictly away from the shredders. Pets you can lock out — kids you can shout at to get the message across — but really the only completely safe method is to not allow them near the machine. If you can't be sure kids and pets won't wander into the vicinity of the shredder, keep the machine's power in the OFF position (not in automatic shred or standby mode) or unplugged when you aren't actively using it.
At the moment the most promising development is that some manufacturers are putting the blades further into the feed path so that there should be no possibility of little fingers getting in there. If you're looking into a home or small-business shredder, check this aspect out, but be prepared to enforce the rules anyway! And lock the door when the machine isn't attended! Much better to be tediously careful than to have to cope with a dreadful mutilation even once.
Some newer shredders have improved upon safety features. For example, Fellowes has introduced Safesense, a technology that automatically disables the shredder to stop shredding when the paper entry is touched or when hands (or pets) come very close to it.