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Terra-Petra’s smoke-testing technique is a key component of any vapor intrusion mitigation system

November 3, 2014

An area of significant concern for Terra-Petra is in the quality assurance and quality control during installation of sub-slab membrane systems, a key part of any vapor intrusion mitigation system. Terra-Petra’s team of deputy inspectors ensure the quality of the mitigation system being installed by routinely checking for any leaks caused by tears or inadequate seals in membrane seams. “Smoke-testing” is a specific technique which Terra-Petra’s inspectors use to check for any deficiencies in a vapor barrier.

Smoke testing is routinely requested by developers, and even selectively opted for by contractors in order to make sure the quality of their membrane installations. Additionally, some governing agencies, including the Los Angeles Department of Building and Safety (LADBS), the Huntington Beach Fire Department (HBFD), and the El Segundo Fire Department mandate smoke testing on 100% of projects within their jurisdiction based on the proven success of this method. The Terra-Petra inspection team is trained to do visual inspections of the membrane prior to smoke testing to check for any obvious breech or tears. This step, which is not typically performed in the industry, adds an extra level of quality control. Any deficiencies are marked for repair.

The membrane installer will then insert the ha key component of any vapor intrusion mitigation systemose of a smoke testing machine, typically attached to a fan or blower, either into the membrane through a small “coupon cut” or into a vent riser.

Coupon cuts are typically applied to spray-applied membranes every 500 square feet and serve a dual purpose of verifying membrane mil thickness and providing an opening for which to perform smoke testing. For sheet membranes, the hose is inserted into the vent riser of the mitigation system.

In both systems, all vent risers are temporarily capped to create pressure under the membrane as the smoke is pumped beneath the membrane. This pressure, which should ideally slightly lift the membrane, is maintained for 15 minutes by the smoke generator as inspectors thoroughly inspect for any leaks. These smoke leaks are indicative of tears in the membrane and are marked for repair then logged in inspection reports for quality control. Smoke testing is one of an inspector’s most important tools in checking the integrity of a vapor barrier system. However, it is important to remember that it is only one tool used to certify the proper sealing of a membrane.

Other important tools used to check for membrane deficiencies include dial calipers, depth gauges, spark testing, and the inspector’s own eyes and judgment. Smoke testing in particular is very effective in checking the seals at penetrations, terminations at footing, and overall coverage of the membrane being installed.

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