Even though the typical use of a playpen is to confine the baby while you're busy, don't leave him alone there. Whether he's inside or out, your baby could crawl or roll into the pocket that forms when the side is down and suffocate.
Playpens—sometimes called play yards by people who think the former raises the specter of baby as prisoner—can be very handy for parents. A playpen offers a safe place to confine a baby, in the kitchen while you're cooking dinner or in the home office while you're working, for example. (Lucky you if your baby plays happily in one and doesn't start to howl the instant she's put in!)
The typical playpen has mesh sides and a wooden floor that bends in the middle for folding. The mesh should have a small weave, less than ¼ inch, so fingers or buttons can't get caught. On wooden models, the space between slats should be no wider than 23/8 inches. It is crucial that playpens be set up properly with sides locked into place.
Since babies like to chew, regularly inspect the vinyl or fabric rail covering in case there are tears or loose pieces that your little teether could break off and choke on.
Playpens are not recommended for babies who weigh more than 30 pounds or who are taller than 34 inches. When it appears your child may be able to climb out, it's time to give up the playpen. Don't put in boxes or other items that a shorter baby could stand on to make an escape.
For babies on the go, portable cribs are becoming increasingly popular. They are lightweight and fold up in a carrying case for travel. Some parents also use them as a substitute for a playpen.
As with a playpen, take care to set up the portable crib properly, locking the sides in place so they won't collapse, and never leaving the sides down. Don't add padding beyond the mattress that comes with it. Stop using it when your child is able to climb out, usually around 30 inches or 30 pounds.