Should every apartment building and condominium complex buy a defibrillator? Should you have one in your house?

Should fire departments and building inspectors try to ensure that one is stuck on the wall of every dwelling, just as they do with fire escapes and smoke detectors?

Many homeowners and building managers are wondering whether they should spend the $2,000 or so these machines cost. One president of a large co-op in a Philadelphia suburb recently put the question this way: "Why should we bother buying an AED [automated external defibrillator] when the police or EMTs will get here in minutes, and we may expose ourselves to lawsuits if the thing is not operated in the right way?"

The folks selling these machines sure think every building should have one. They are all over the Internet and the airwaves plugging the machines' lifesaving potential. Of course, selling them at two grand a pop to every home, apartment building, office, airport, stadium, sports arena, auditorium, and swimming pool in America would earn them gazillions.

But the more objective answer to the defibrillator question is, as is so often the case, "It depends."

The devices are helpful in kick-starting hearts when they are having certain kinds of electrical trouble. Most cardiac arrests are caused by heart rhythms that can be corrected with defibrillation. But if a heart stops because it has no electrical activity, or because the heart muscle is too far gone to conduct electricity, a machine that shoots a blast of electricity into it won't do any good.

The usefulness of automated external defibrillators depends on the location and the people living there. If there are a lot of older people present, it makes some sense, since they are at a higher risk of conditions that can lead to cardiac arrest.

While emergency personnel do carry defibrillators, time is an important factor in the outcome of a heart attack. If it would take firefighters or paramedics a long time to get a defibrillator to you - because you live in a heavily congested area, on the higher floors of a tall building, or in a rural location - that may make buying one worthwhile.

As for lawsuits over defibrillator use, they are not likely to be winners. Those who make a good-faith effort to follow the instructions should be safe from the slip-and-fall crowd.

These devices are not, however, for everyone or everywhere. Most homes and many apartment buildings don't need one.

What makes as much or more sense is to train everyone in your house or building in CPR and to make sure there is always a phone nearby in case of trouble. But since no one makes a lot of money pushing these basic safety steps, defibrillators are being made to seem a bit more important than they probably are for a lot of people.

Arthur Caplan is the director of the Center for Bioethics at the University of Pennsylvania, where Dr. James Kirkpatrick is an assistant professor in the division of cardiology at the Perelman School of Medicine.