Bar code technology is very common in non-security applications but it is seldom the technology of choice for security. The card is swiped so that the cell inside the reader can read the bar code through a lens. Visible bar code technology has obvious security drawbacks. For example, cards can be duplicated with a photocopier or by faxing. Although it is possible to mask the bar code with a filter that makes duplication more difficult, most buyers prefer more secure technologies. The cards have an average life of 18 to 30 months. The reader lens requires cleaning once a year on average, or more if installed in dusty environments such as parking lots.