TIA-222-G suggests maintenance and condition assessment should be performed at least once every three years for guyed towers and once every five years for self-supporting towers. Towers used for essential communications or those that represent a high hazard in the event of failure (Class III structures), towers in coastal regions or corrosive environments, or towers subjected to frequent vandalism require more frequent assessment and maintenance. Towers should also be assessed after severe seismic events and wind and ice storms.