Plug-in electrical outlet covers, a basic home safety feature for millions of parents of young children, may provide a false sense of security in many homes, a Philadelphia researcher has found.

Marcella Ridenour, a senior researcher at Temple University's Biokinetics Laboratory, found that a group of 2- and 4-year-olds were able to remove most covers in an average of about 20 seconds.She tested three common designs of the devices with 37 children, 2 and 4 years old, and a control group of young adults.

She found that virtually all the 4-year-olds could remove at least one model of cover within two minutes, and 42 percent were able to remove them all.

Among the 2-year-olds, one model was removed by almost all the children, and a third could take another cover off consistently. One in five of the toddlers succeeded in removing the third type of protector.

Virtually all the adults, college students ranging in age from 19 to 25 years of age, were able to remove all styles of outlet cover in one to four seconds.

It took the children from two to 10 seconds to remove the easiest style of outlet cover, and those who were successful with the other two types of protectors took only an average of 23 to 38 seconds to pop them off.

"None of these devices are intended to be impossible for children to remove given unlimited time; they're meant to be difficult enough to slow down access for a child that's unsupervised for a few minutes," Ridenour said.

"When you child-proof a product, you want it to be very difficult for children to remove but very easy for adults to remove or they won't buy it or use it," she added. "Clearly, the products we tested aren't doing what they're sold to do."

Labels on packages of the outlet protectors typically do caution parents that children may be able to thwart the devices but don't say how quickly or easily that may happen, the researcher noted.

Reports collected from hospital emergency rooms by the federal Consumer Product Safety Commission indicate that children are most often injured playing with electrical sockets when parents are preparing meals and that the objects most often put in the sockets are keys and hairpins.

Commission records show 155 children aged 4 and under have been injured by outlets since 1990, but the reports include only those youngsters brought to emergency rooms. And the records do not indicate whether outlet covers were removed before the accidents occurred. Typically, the injuries were electrical shock, often coupled with first or second degree burns to fingers and hands.

The Temple research was published recently in a journal called Perceptual and Motor Skills.

Ridenour, who has studied child safety issues on a number of products in the past, said she took up the outlet covers test "because I kept hearing from friends who were parents that they weren't working very well."

For the lab experiment, the electric receptacles were disguised with clown face stickers and the covers were painted as clown noses to make ordinary protectors less attractive as toys in the children's homes later. Lab assistants removed the covers several times in front of the children, simulating what a mom might do while vacuuming, for instance, and then the children were asked to remove the protectors themselves.

Ridenour said that unlike toys and car seats, there are no published standards for the design or testing of outlet covers, nor any requirement for labeling the devices on how they should be used or at what age they're effective.

She pointed out that parents need to test how difficult outlet covers are to remove. Her study found that up to four times as much pressure was needed to remove the most resistant style of outlet cover compared with the easiest model. Older outlets may not hold the plastic prongs as tightly, and outlet boxes that aren't mounted flush with walls may also offer a poorer fit for the devices.

She selected the styles of outlet protectors to test by scouting what models were most often sold in toy stores, baby stores and department stores.

"There are a number of other protective devices out there, including some outlets with built-in guards that can be installed, and some that must be twisted or slid aside before anything can be inserted, but these are by far the most common," Ridenour said.