Impacts to indoor air quality from volatile organic compounds (VOCs) have been receiving greater attention recently due to a growing awareness of vapor intrusion (VI) from underground oil and chemicals. VI occurs when chemicals spilled on the ground migrate under structures and then volatilize up into indoor air. After a recent residential basement oil spill I was called in to provide a second opinion on why high indoor air VOC concentrations persisted in the home after the cleanup had been completed. Some of the results were very surprising.
Locating VOCs in the Basement
Following the release, a well qualified response contractor had conducted a thorough cleanup. The remediation included removing portions of the floor slab, wall board, wood framing and most other building materials that had been contacted by the oil. Despite the cleanup, indoor air concentrations in the basement and first floor of the house exceeded the Massachusetts Department of Environmental Protection criteria.
The contractor suspected the problem was the first course of concrete chimney blocks, which had likely absorbed oil in the aftermath of the spill. The oil in the blocks was now likely volatilizing into the air. Removing and replacing the contaminated blocks presented an obvious structural challenge so initially an epoxy sealant was applied to the entire chimney to prevent further oil volatilization. However, indoor air testing conducted after the epoxy had cured showed that indoor air concentrations remained stubbornly high.
To assess the cause of the indoor air levels, I visited the subject home with a ppbRAE to see if it would help me locate the source of the organic vapors. Once in the basement, it did not take long to discover that the epoxy sealant was not preventing VOC migration out of the concrete chimney blocks; the blocks were still off-gassing VOCs to the basement air. While there were also a few pieces of previously unidentified wood framing off-gassing VOCs, the concrete blocks looked to be the main culprit.
But What’s Going on Upstairs?
With the basement VOC source identified, I went upstairs to check on first floor; what I found there was completely unexpected. While ambient basement air VOC readings had been just above zero (at some distance from the chimney), ambient levels on the first and second floors were about 200 ppb! How could this be? I walked through the house with the home owner trying to identifying potential VOC sources. After an hour of looking I hadn’t been able to identify a source and almost everywhere in the occupied space I was measuring 200 +/- 40 ppb of VOCs in the breathing zone air; there were no odors. Big mystery!
Finally, on a high book shelf in the living room I noticed two glass hurricane lamps; each containing several ounces of clear liquid lamp oil. When I held the tip of the ppbRAE probe over the glass lamp chimneys the instrument’s numerical readout shot up; the mystery of the upstairs VOC source was seemingly solved! And the source was completely unrelated to the basement oil spill.
What is in lamp oil that causes such a strong response on the ppbRAE? From my limited on-line research, there does not appear to be a commonly accepted formula for lamp oil. At one time kerosene was used, but this now seems less common except in outdoor settings. Whale oil was also once used, a practice now thankfully in the past. The oil in these lamps had no odor, but beyond that I do not have any information on what it was. I did not collect a sample for lab testing, so I do not know specifically what the ppbRAE was responding to.
This experience was a good reminder of just how sensitive today’s air monitoring equipment has become. Even very small contributions from sources that do not seem particularly volatile can have a dramatic impact on indoor air testing measurements. It is important to keep a watchful eye out for unanticipated VOC sources when conducting indoor air testing.