ANSI/ASHRAE Standard 62.1-2007 is the latest edition of the standard. It applies to all spaces intended for human occupancy except those within single-family houses, multifamily structures of three stories or fewer above grade, vehicles, and aircraft. The standard defines requirements for ventilation and air-cleaning system design, installation, commissioning, and operation and maintenance. The 2007 edition combines Standard 62.1-2004 and the eight approved and published addenda to the 2004 edition, thereby providing an easy-to-use consolidated standard. Specific information on the content of each addendum and approval dates for each addendum are included in informative Appendix I. First published in 1973, Standard 62.1 is now updated on a regular basis using ASHRAE's continuous maintenance procedures. Standard 62.1 has undergone some key changes over the years, reflecting the ever-expanding body of knowledge, experience, and research related to ventilation and air quality. While the purpose of the standard has remained consistent--to specify minimum ventilation rates and other measures intended to provide indoor air quality that is acceptable to human occupants and that minimizes adverse health effects--the means of achieving this goal have evolved.