-----Original Message----- I don't know what an average lifespan might be; I would think it depends upon the wattage of the tube it is filtering. My understanding as to why the filters expire is that they become saturated, i.e., the filters absorb the UV rays and they can only hold so much. ____________ Actually when this happens you can take the sleeves down and rinse them out over a pail and re-use them. It cleans all the old UV rays out of them and makes them good as new. There's even a drop-off bin at one of the medical clinics in town where they recycle the old UV rays and use them to treat Seasonally Affective Disorder during the winter so the whole thing is completely environmentally friendly. Jeff "Friday comes early at the Archives" O'Brien ____________________________________ J. Jeffrey O'Brien City of Saskatoon Archivist Tel: 306-975-7811 Fax: 306-975-2612 2002 Calendars on sale now! For ordering information and to see a preview, visit us at: http://www.city.saskatoon.sk.ca/org/clerks_office/archives/ar-gall.asp#2002c alendars A posting from the Archives & Archivists LISTSERV List! To subscribe or unsubscribe, send e-mail to [log in to unmask] In body of message: SUB ARCHIVES firstname lastname *or*: UNSUB ARCHIVES To post a message, send e-mail to [log in to unmask] Or to do *anything* (and enjoy doing it!), use the web interface at http://listserv.muohio.edu/archives/archives.html Problems? Send e-mail to Robert F Schmidt <[log in to unmask]>