The Loudoun County Board of Supervisors voted Tuesday to consider adopting an ordinance that would require burglar alarm users to register with the county, give them two false alarms without penalty and fine them for each one after that.

The proposed ordinance is meant to stem false burglar alarms, which account for 99 percent of the 66,000 burglar alarms that sheriff's deputies have responded to since 1996, according to a 2002 study conducted by the Sheriff's Office and the county's information technology department.

In 2002, deputies and dispatchers spent more than 5,795 hours responding to false alarms, the equivalent of about 15 hours a day. That cost the office $138,933 in personnel costs alone, the study found.

The false alarms keep officers from providing backup to their colleagues and protecting the public, said Maj. Scott Waddell.

"This is causing a safety issue for the rest of the county," he said. "It's increasing our response time for other calls to serve that are valid."

According to the Sheriff's Office, which recommended the ordinance, more than 95 percent of jurisdictions nationwide and nearly all those in the Washington area have false alarm policies. Waddell said the proposed ordinance is modeled in part after one in Montgomery County, where false alarms have dropped about 50 percent.

"We're hoping for the same success as Montgomery County," Waddell said.

Loudoun County Fire and Rescue Services is gathering statistics on false fire alarms and might propose a separate ordinance later, said Matt Partlow, acting assistant fire chief.

Under the proposed false burglar alarm ordinance, residential alarm users would be required to pay $30 to register their systems and a $10 renewal fee every two years. Commercial alarm users would pay an initial registration fee of $45 and a renewal fee of $20 every two years.

Users would be fined $50 for a third false alarm, and fines would increase with each one after that, up to $1,000 for residential users and $4,000 for business users. It would take 23 false alarms for a residential users and 73 false alarms for businesses to reach their respective maximum fines.

The ordinance would also impose the fees and fines on public facilities, including schools, which set off a disproportionate number of false alarms, Waddell said. In 2002, Park View High School in Sterling, with 67 false alarms, led the "top 10 offenders" list, he said. Stone Bridge High School in Ashburn came in second with 61 false alarms. Most others on the list were businesses.

The Sheriff's Office estimates that enforcing the proposed ordinance, which calls for new software and a staff of two to handle billing and registration, would cost the county about $182,000 over the next two years. But the fees and fines from alarm users would easily cover that, Waddell said. The Sheriff's Office said registration fees from residential alarms alone would generate more than $120,000 in 2005.

Also, Waddell said, "if it ever got to the point where there were not enough activations to pay for the [employees], you wouldn't need so many people in the unit."

False alarms usually occur when alarm systems are broken or an alarm is set before everyone has left a building, Waddell said. The ordinance could inspire alarm users to fix their systems or use them more carefully, he said.

The Sheriff's Office estimates that there are more than 5,000 alarm users in the county.

The supervisors will hold a public hearing on the proposed ordinance Dec. 14 and vote Jan. 4 on whether to adopt it.