Combustion Safety Simplified Test Protocol Field Study

Executive Summary


Combustion safety testing is an important step in the process of upgrading homes for energy efficiency. Field practitioners use several approaches based on published standards. Researchers have indicated that the test procedures in use are complex to implement in the field and provide too many false positives—i.e., too many failures that do not relate to long-term problems in the home. Failures often mean that money is diverted from energy-efficiency measures—or upgrades may not be made at all—if the program does not include remediation of safety issues. In this report the U.S. Department of Energy’s Building America research teams Partnership for Advanced Residential Retrofit and NorthernSTAR provide a simplified test procedure (STP) that is easier to implement and should produce fewer false positives. The report includes a survey of state weatherization agencies on combustion safety issues, details of a field data collection instrumentation package, summary of data collected over 7 months, data analysis, and results. 

The project provides several key results. State weatherization agencies do not generally track combustion safety failures. The data from those that do suggest limited actual evidence that combustion safety failures due to spillage from nondryer exhaust are common and that only a very small number of homes are subject to the failures.

Based on sequential application of the tests in the field, the STP identifies problem houses as effectively as the worst-case procedures.

The project team collected field data over a period of 7 months on 11 houses that indicated failures under the STP. Of these, 2 houses that demonstrated prolonged and excessive spillage were also the only 2 with venting systems that were out of compliance with the National Fuel Gas Code. The remaining homes experienced spillage that only occasionally extended beyond the first minute of operation. Combustion zone depressurization, outdoor temperature, and operation of individual fans all provide statistically significant predictors of the low level of spillage observed in these houses.

The authors concluded that vent system inspection should be the primary element of any combustion safety evaluation, and auditors need appropriate training to recognize vent system deficiencies. Carbon monoxide monitoring is an important part of the test and should also be included. The STP is an improvement over the worst-case approaches, but it still overpredicts the occurrence of problem houses. More work is needed to establish a more-predictive short-term test method.

These results are based on the 17 states that responded to the survey and the 11 houses instrumented in the project over 7 months. Technology transfer has already begun in the form of contributing many of the recommendations in the STP to the Building Performance Institute-1200 standard that was published in the spring of 2015.


This report is prepared for The National Renewable Energy Laboratory on behalf of the U.S. Department of Energy’s Building America Program


Full report (PDF):
Combustion Safety Protocol