In many residential building retrofit programs, air tightening to increase energy efficiency is constrained
by concerns about related impacts on the safety of naturally vented combustion appliances. Tighter
housing units more readily depressurize when exhaust equipment is operated, making combustion
appliances more prone to backdraft or spillage. Several test methods purportedly assess the potential for
depressurization-induced backdrafting and spillage, but these tests are not robustly reliable and repeatable
predictors of venting performance, in part because they do not fully capture weather effects on venting
performance. The purpose of this literature review is to investigate combustion safety diagnostics in
existing codes, standards, and guidelines related to combustion appliances. This review summarizes
existing combustion safety test methods, evaluations of these test methods, and also discusses research
related to wind effects and the simulation of vent system performance. Current codes and standards
related to combustion appliance installation provide little information on assessing backdrafting or
spillage potential. A substantial amount of research has been conducted to assess combustion appliance
backdrafting and spillage test methods, but primarily focuses on comparing short-term (stress) induced
tests and monitoring results. Monitoring, typically performed over one week, indicated that combinations
of environmental and house operation characteristics most conducive to combustion spillage were rare.
Research, to an extent, has assessed existing combustion safety diagnostics for house depressurization,
but the objectives of the diagnostics, both stress and monitoring, are not clearly defined. More research is
also needed to quantify the frequency of test "failure" occurrence throughout the building stock and
assess the statistical effects of weather (especially wind) on house depressurization and in turn on
combustion appliance venting. Incorporating weather variations and house ventilation system
characteristics in existing simulation software may assist such analyses and with developing a more
reliable diagnostic for use on-site.