Today there is an increased interest in ventilation effectiveness being stimulated by the tremendous increase in the interest of indoor air quality and the general lack of information regarding the impact of ventilation effectiveness upon indoor air quality.

A new standard was developed to define tracer gas procedures for measuring air change effectiveness. Standard 129, Standard Method of Measuring Air Change Effectiveness, defines two tracer gas test procedures: tracer gas step up test procedure and tracer gas decay procedure. Standard 129 further defines three sampling methods: automated line sampling; grab sampling; integrated bag sampling.

RP-891 was undertaken with these objectives:
1.) to obtain information on the practicality of the measurement procedures and to obtain recommendations that can be used to improve future versions of ASHRAE Standard 129
2.) to quantify the precision of measured values of air change effectiveness, when the measurement procedures specified in the draft of Standard 129 are utilized.