Here is part of a "white paper" we use help educate concerned users about ozone. Some of the sub and super scripts may not fare well in transmission. -------------------------------------------------------------------------------- ------------------------------------------------------------------
BACKGROUND Ozone (O(superscript: 3)) is a gas found close to the surface of the earth, and in higher concentrations in the upper atmosphere. The primary source of ozone is atmospheric oxygen under the influence of the sun's ultraviolet radiation. Ozone is also formed from electrical discharges, or arcs, such as lightning. Ozone contributes to the characteristic "smell" after a thunderstorm. Naturally occurring ozone levels range from 0.005 to 0.05ppm at the earth's surface, and up to 11ppm at 93,000 feet elevations (ppm = parts per million). Electrical equipment produces ozone when arcing occurs. Examples range from arc welders to common light switches. Office products using electrophotographic (EP) processes to print documents generate detectable ozone if coronas are used to charge the photoconductor. As a result, many early copiers, fax machines, and EP printers emitted detectable levels of ozone. While man-made ozone is small compared to nature's levels, it typically occurs indoors, often in confined areas, and may be noticeable to human operators or by-standers. STANDARDS Ozone can be an irritant to some people at fairly low concentrations. As a result, various world health organizations have established recommended ozone concentration limits. These are often stated as a time weighted average (TWA) over an 8 hour period. The international standard for the safety of Information Technology Equipment, IEC 950, recommends a TWA limit of 0.1ppm (0.2mg/m(superscript: 3)). The American Conference of Governmental and Industrial Hygienists (ACGIH) suggests the same limits where light work is performed, and a limit of 0.05ppm (0.1mg/m(superscript: 3)) where heavy work is being performed. One test protocol used is defined by Underwriter's Laboratory standard UL 478 Section 45. George Alspaugh Lexmark International --------- This message is coming from the emc-pstc discussion list. To cancel your subscription, send mail to majord...@ieee.org with the single line: "unsubscribe emc-pstc" (without the quotes). For help, send mail to ed.pr...@cubic.com, j...@gwmail.monarch.com, ri...@sdd.hp.com, or roger.volgst...@compaq.com (the list administrators).
