Credit that to the dramatic growth of cell phones and other digital technologies. To deploy a wireless network, telecommunications companies have to mount antennas to towers, buildings, or other tall structures.

Rooftops, as a result, have become prime real estate. Real estate owners and managers typically sell unused rooftop space to antenna management companies, who locate users and sell transmission rights to telecommunications companies.

There are more than 210,000 cellular sites and about 20,000 telecom central offices nationwide, according to industry statistics, and the number is growing about 11% a year.

But the National Association of Tower Erectors say safety may be secondary to profit. The organization warns that many property owners are oblivious to the details: they don't know who is building the broadcast towers on their rooftops or whether the workers are performing safely.

The trade association has issued two tower safety checklists includes the latest industry best practices and standards. The checklists are based on NATE's 13 years of experience providing the safety training and materials to tower climbers and maintenance crews.

NATE is encouraging tower owners and operators to use the checklist to improve the way they build and maintain towers. The checklist addresses hiring safe contractors, keeping a safe tower site and keeping towers in good working order.

The recommendations include:

• Find out whether tower service companies have a written safety and health program that meets Occupational Safety and Health Administration (OSHA) rules;
• Lowering RF emitters to safe levels or turning them off before allowing tower climbers on the site;
• Coordinate with tenants and other users on the tower to ensure their equipment is free from known safety hazards, including RF emissions, before allowing climbers on the tower.
• Keep guy cable tension wires within manufacturers' specifications.