threshold limit value
This is a guideline value defined by the American Conference of Governmental Hygienists to establish the airborne concentration of a potentially toxic substance to which it is believed that healthy working adults may be exposed safely through a 40 hour working week and a full working life. This concentration is measured as a time weighted average concentration. They are developed only as guidelines to assist in the control of health hazards and are not developed for use as legal standards.
Selected threshold limit value links: