Access control is a major problem for businesses large and small. Companies with high-tech access control systems - key cards, fingerprint- or retina scanners, etc. - can easily reprogram access codes and delete former employees from the data base. But even smaller businesses that rely on the security provided by a good, traditional lock-and-key system need to update their access controls regularly. This is an issue whether you use padlocks, cylinder locks, or police locks.

The first step is to conduct a regular Key Audit to review the status and location of every key, making sure that no unauthorized person has one. In small businesses with few employees, this can be a fairly simple process and one that's sufficient to ensure access control.

If your company has more than a few employees, though, an audit might not be enough. A former employee - especially a resentful fired one - might still hold a key, inadvertently or deliberately. He might have "lost it," ? or have made a duplicate before returning it.

Some businesses protect against unauthorized duplication by having every key stamped "Do not duplicate;" ? reputable locksmiths will refuse to make an unauthorized copy. Unfortunately, there are key cutters who will ignore that stamp, and others (especially at high-volume big-box stores) don't have time to (or simply don't) pay attention to such strictures.

Some keys are harder to copy than others. Medeco keys are impossible to duplicate except by licensed Medeco dealers, and then only with the permission of the registered owner. That protection eliminates the possibility of someone copying a key before returning it on request. But even Medeco locks are vulnerable to the former employee who "lost" ? his key and therefore can't turn it in.

The safest way to ensure that only authorized people have keys is by repinning locks from time to time, so that old keys no longer work. After all, it's not only disgruntled people who hold on to keys. At one point, I had keys to three small businesses where I'd once worked, and where I was still friendly with the owners. Keeping the keys was not for dishonest reasons, just rather dishonorable ones: it was convenient when I was in the neighborhood to be able to go in, even when they were closed, to use the bathroom or make a quick phone call (this was before cell phones). One of those keys still worked five years after I'd left!

If you haven't conducted a Key Audit recently, do so. And if there's any possibility that a former employee (or maybe a current employee's disgruntled ex-) or even someone like me, has an unauthorized key, you need to call to have the locks changed. The cost of repinning and replacing a few keys - or even a large number of them - is far less than the loss you could face as a result of unauthorized access.

All the above holds true for residences, too. Think of all the people who have had keys to your apartment over the years - the super (or a series of them), a maid or cleaning service, caterers, the landlord, a neighbor who's moved away, dog walkers, careless teenagers who lent their key to their best friend . . . .

It's probably time to make a change - before you wish you had.